Looks like the fail-safe for Python environment for weboob plugin doesn't work as it should. I'll look into it.

Any update on this?

The last build to work was 876 (KMyMoney-5.1.1-bbdd7eb-x86_64.appimage)

*** Bug 439867 has been marked as a duplicate of this bug. ***

Git commit 82ab3fefe2971caddc050b7f336786dad2071cba by Dawid Wróbel.
Committed on 19/07/2021 at 10:38.
Pushed by wrobelda into branch 'master'.

Make woob plugin failsafe on Python issues

- show error messages if Python or Woob fails to load
- do some additional code refactoring
FIXED-IN: 5.1.3

M  +0    -1    kmymoney/plugins/woob/dialogs/mapaccountwizard.cpp
M  +47   -21   kmymoney/plugins/woob/interface/woobinterface.cpp
M  +8    -1    kmymoney/plugins/woob/interface/woobinterface.h
M  +56   -27   kmymoney/plugins/woob/woob.cpp
M  +1    -0    kmymoney/plugins/woob/woob.h

https://invent.kde.org/office/kmymoney/commit/82ab3fefe2971caddc050b7f336786dad2071cba

All,

Please test this build once it completes:
https://binary-factory.kde.org/job/KMyMoney_Stable_Appimage_Build/913/

Actually, my bad, this is not a correct build. Let me get back to you.

Git commit 2f9af3dca81fe24b70e71e1ed11d7bff3b2d3e99 by Dawid Wróbel.
Committed on 19/07/2021 at 13:02.
Pushed by wrobelda into branch '5.1'.

Make woob plugin failsafe on Python issues

- show error messages if Python or Woob fails to load
- do some additional code refactoring
FIXED-IN: 5.1.3

M  +0    -1    kmymoney/plugins/woob/dialogs/mapaccountwizard.cpp
M  +49   -26   kmymoney/plugins/woob/interface/woobinterface.cpp
M  +8    -1    kmymoney/plugins/woob/interface/woobinterface.h
M  +57   -28   kmymoney/plugins/woob/woob.cpp
M  +2    -1    kmymoney/plugins/woob/woob.h

https://invent.kde.org/office/kmymoney/commit/2f9af3dca81fe24b70e71e1ed11d7bff3b2d3e99

Try this build once its complete:
https://binary-factory.kde.org/job/KMyMoney_Stable_Appimage_Build/914/

Tried ./KMyMoney-5.1.2-47e90cc-x86_64.AppImage which still fails for me on openSUSE Leap 15.2:

:
:
Loading "/tmp/.mount_KMyMona7wMm4/usr/plugins/kmymoney/woob.so"
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'python3'
  isolated = 0
  environment = 1
  user site = 1
  import site = 1
  sys._base_executable = '/usr/bin/python3'
  sys.base_prefix = '/usr'
  sys.base_exec_prefix = '/usr'
  sys.platlibdir = 'lib'
  sys.executable = '/usr/bin/python3'
  sys.prefix = '/usr'
  sys.exec_prefix = '/usr'
  sys.path = [
    '/usr/lib/python39.zip',
    '/usr/lib/python3.9',
    '/usr/lib/lib-dynload',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f8d1e353540 (most recent call first):
<no Python frame>

tried 914 on Kubuntu 18.04 still not working

Painter::begin: Paint device returned engine == 0, type: 2
WebConnect: Try to connect to WebConnect server
WebConnect: Connect to server failed
WebConnect: Starting server failed. Try to remove stale socket.
WebConnect: Running in server mode
Found an 'html' folder with CSS files: "/tmp/.mount_914_KMF2VmMs/usr/bin/../share/kmymoney/html/"
System icon theme as reported by QT:  "breeze-dark"
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QFSFileEngine::open: No file name specified
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/budgetview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/checkprinting.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/csvexporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/csvimporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/forecastview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/gncimporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/icalendarexporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kbanking.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_checkprinting.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_csvimporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_forecastview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_icalendarexporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_qif.so" Validity false
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_reportsview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kcm_xmlstorage.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/konlinetasks_sepa.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/ofximporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/onlinejoboutboxview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/qifexporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/qifimporter.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/reconciliationreport.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/reportsview.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/sqlstorage.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/woob.so" Validity true
Located plugin "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/xmlstorage.so" Validity true
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/budgetview.so"
Plugins: budgetview loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/checkprinting.so"
Plugins: checkprinting loaded
QIODevice::read (QFile, "/usr/share/checkprinting/check_template.html"): device not open
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/csvexporter.so"
Plugins: csvexporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/csvimporter.so"
Plugins: csvimporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/forecastview.so"
Plugins: forecastview loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/gncimporter.so"
Plugins: gncimporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/icalendarexporter.so"
Plugins: icalendarexporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/kbanking.so"
"Plugins: kbanking loaded, build with (5.6.0stable-0/6.2.10.0stable), run with (5.6.0.0/6.2.10.0)"
3:2021/07/21 18-58-07:(null)(12849):/home/appimage/appimage-workspace/deps-build/ext_aqbanking/ext_aqbanking-prefix/src/ext_aqbanking/src/libs/aqbanking/banking_update.c:  610: No AqBanking config folder found at [/home/eagleboy/.aqbanking/settings6/users] (-1)
3:2021/07/21 18-58-07:(null)(12849):/home/appimage/appimage-workspace/deps-build/ext_aqbanking/ext_aqbanking-prefix/src/ext_aqbanking/src/libs/aqbanking/banking_update.c:  610: No AqBanking config folder found at [/home/eagleboy/.aqbanking/settings/users] (-1)
3:2021/07/21 18-58-07:(null)(12849):/home/appimage/appimage-workspace/deps-build/ext_aqbanking/ext_aqbanking-prefix/src/ext_aqbanking/src/libs/aqbanking/banking_update.c:  411: There is no old settings folder, need initial setup
7:2021-07-21 18:58:07:aqbanking started
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/ofximporter.so"
Plugins: ofximporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/onlinejoboutboxview.so"
Plugins: onlinejoboutboxview loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/qifexporter.so"
Plugins: qifexporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/qifimporter.so"
Plugins: qifimporter loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/reconciliationreport.so"
Plugins: reconciliation report loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/reportsview.so"
Plugins: reportsview loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/sqlstorage.so"
Plugins: sqlstorage loaded
Loading "/tmp/.mount_914_KMF2VmMs/usr/plugins/kmymoney/woob.so"
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'python3'
  isolated = 0
  environment = 1
  user site = 1
  import site = 1
  sys._base_executable = '/usr/bin/python3'
  sys.base_prefix = '/usr'
  sys.base_exec_prefix = '/usr'
  sys.platlibdir = 'lib'
  sys.executable = '/usr/bin/python3'
  sys.prefix = '/usr'
  sys.exec_prefix = '/usr'
  sys.path = [
    '/usr/lib/python39.zip',
    '/usr/lib/python3.9',
    '/usr/lib/lib-dynload',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f55dda36500 (most recent call first):
<no Python frame>

I can confirm the fix does not work on WIN10 either. Tested with both stable (v5.1.2-51a7a9f77) and master builds (Version v5.1.80-4ff353925).

Error message below: 

Microsoft Windows [Version 10.0.19043.1165]
(c) Microsoft Corporation. All rights reserved.

C:\Users\Cvet>C:\Users\Cvet\Downloads\kmymoney-5.1-1116-windows-msvc2019_64-cl\bin\kmymoney.exe

C:\Users\Cvet>WebConnect: Try to connect to WebConnect server
WebConnect: Connect to server failed
WebConnect: Running in server mode
Found html dir(s): ("C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/data/kmymoney//html/")
Found an 'html' folder with CSS files: "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/data/kmymoney//html/"
System icon theme as reported by QT:  ""
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::begin: Paint device returned engine == 0, type: 2
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/budgetview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/checkprinting.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/csvexporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/csvimporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/forecastview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/gncimporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/icalendarexporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_checkprinting.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_csvimporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_forecastview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_icalendarexporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_qif.dll" Validity false
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_reportsview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/kcm_xmlstorage.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/konlinetasks_sepa.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/ofximporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/onlinejoboutboxview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/qifexporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/qifimporter.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/reconciliationreport.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/reportsview.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/sqlstorage.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/woob.dll" Validity true
Located plugin "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/xmlstorage.dll" Validity true
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/budgetview.dll"
Plugins: budgetview loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/checkprinting.dll"
Plugins: checkprinting loaded
QIODevice::read (QFile, "C:\Users\Cvet\Downloads\km\bin\data\checkprinting\check_template.html"): device not open
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/csvexporter.dll"
Plugins: csvexporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/csvimporter.dll"
Plugins: csvimporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/forecastview.dll"
Plugins: forecastview loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/gncimporter.dll"
Plugins: gncimporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/icalendarexporter.dll"
Plugins: icalendarexporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/ofximporter.dll"
Plugins: ofximporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/onlinejoboutboxview.dll"
Plugins: onlinejoboutboxview loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/qifexporter.dll"
Plugins: qifexporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/qifimporter.dll"
Plugins: qifimporter loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/reconciliationreport.dll"
Plugins: reconciliation report loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/reportsview.dll"
Plugins: reportsview loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/sqlstorage.dll"
Plugins: sqlstorage loaded
Loading "C:/Users/Cvet/Downloads/kmymoney-5.1-1116-windows-msvc2019_64-cl/bin/kmymoney/woob.dll"
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'python'
  isolated = 0
  environment = 1
  user site = 1
  import site = 1
  sys._base_executable = 'C:\\Users\\Cvet\\Downloads\\kmymoney-5.1-1116-windows-msvc2019_64-cl\\bin\\kmymoney.exe'
  sys.base_prefix = ''
  sys.base_exec_prefix = ''
  sys.executable = 'C:\\Users\\Cvet\\Downloads\\kmymoney-5.1-1116-windows-msvc2019_64-cl\\bin\\kmymoney.exe'
  sys.prefix = ''
  sys.exec_prefix = ''
  sys.path = [
    'C:\\Programs\\Anaconda3\\python38.zip',
    '.\\DLLs',
    '.\\lib',
    'C:\\Users\\Cvet\\Downloads\\kmymoney-5.1-1116-windows-msvc2019_64-cl\\bin',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00004294 (most recent call first):
<no Python frame>
QEventDispatcherWin32::wakeUp: Failed to post a message (Invalid window handle.)