The archive "/usr/lib/qt/plugins/kcm_knote.so" is there but it still doesn't work. Maybe just a slight problem with a configuration in the package?.

Confirmed on:
Operating System: Solus 4.1
KDE Plasma Version: 5.20.4
KDE Frameworks Version: 5.77.0
Qt Version: 5.15.2
Kernel Version: 5.10.4-165.current

I rebuild it here and it works fine.
Perhaps a distro problem here.
Regards

Hello! :D
Or maybe a kernel thing?
Justin Zobel confirmed the issue on Solus OS.
By the way, which distro are you using Laurent Montel?
Are you using the latest stable kernel? (5.10.4 apparently)

Not a distro problem (and nothing to do with the kernel), this is caused by https://invent.kde.org/pim/knotes/-/commit/0e470b8fc8339da31050400e415f75ba80ef6698

(In reply to Antonio Rojas from comment #5)
> Not a distro problem (and nothing to do with the kernel), this is caused by
> https://invent.kde.org/pim/knotes/-/commit/
> 0e470b8fc8339da31050400e415f75ba80ef6698

configdialog/knoteconfigdialog.cpp is exported:
"class KNOTES_EXPORT KNoteConfigDialog : public KCMultiDialog"
it's includes in 

set(libknotesprivate_config_lib_SRCS
    configdialog/knotesimpleconfigdialog.cpp
    configdialog/knoteconfigdialog.cpp
    configdialog/knotedisplayconfigwidget.cpp
    configdialog/knoteeditorconfigwidget.cpp
    configdialog/knotecollectionconfigwidget.cpp
    )

set(libknotesprivate_lib_SRCS
    ${libknotesprivate_config_lib_SRCS}
    ${libknotesprivate_print_lib_SRCS}
    knoteedit.cpp
    knotes_debug.cpp
    notes/knotedisplaysettings.cpp
    utils/knoteutils.cpp
    notes/knoteinterface.cpp
    notes/knotesmigrateapplication.cpp
    finddialog/knotefinddialog.cpp
    )

add_library(knotesprivate ${libknotesprivate_lib_SRCS} ${libknotesprivate_kcfg_lib_SRCS} )

target_link_libraries(kcm_knote knotesprivate KF5::AkonadiCore  KF5::KCMUtils KF5::NewStuff notesharedprivate KF5::AkonadiNotes KF5::PimCommon KF5::I18n KF5::AkonadiWidgets)


(and it builds/works fine from a fresh build).

And on windows it complains as it's in already in lib.

So perhaps there is an explaination but for the moment I didn't see it.

(In reply to Laurent Montel from comment #6)
> So perhaps there is an explaination but for the moment I didn't see it.

The problem is that the linker will remove the libknotesprivate link from kcm_knote.so when using --as-needed (as it's done in most distros to prevent massive overlinking) because it doesn't use any of its public symbols.

(In reply to Antonio Rojas from comment #7)
> (In reply to Laurent Montel from comment #6)
> > So perhaps there is an explaination but for the moment I didn't see it.
> 
> The problem is that the linker will remove the libknotesprivate link from
> kcm_knote.so when using --as-needed (as it's done in most distros to prevent
> massive overlinking) because it doesn't use any of its public symbols.

class KNOTES_EXPORT KNoteConfigDialog it's exported so it's public symbol for me no ?

(In reply to Laurent Montel from comment #8)
> class KNOTES_EXPORT KNoteConfigDialog it's exported so it's public symbol
> for me no ?

But it's not used in any of the kcm_knote sources:

$ grep KNoteConfigDialog configdialog/knotedisplayconfigwidget.cpp configdialog/knoteeditorconfigwidget.cpp configdialog/knotecollectionconfigwidget.cpp

[nothing]

(In reply to Antonio Rojas from comment #9)
> (In reply to Laurent Montel from comment #8)
> > class KNOTES_EXPORT KNoteConfigDialog it's exported so it's public symbol
> > for me no ?
> 
> But it's not used in any of the kcm_knote sources:
> 
> $ grep KNoteConfigDialog configdialog/knotedisplayconfigwidget.cpp
> configdialog/knoteeditorconfigwidget.cpp
> configdialog/knotecollectionconfigwidget.cpp
> 
> [nothing]

so knotesprivate is not useful and KNoteConfigDialog is not useful here :) 
So it's not useful => remove by distro/compile (so not a knotes bugs as if I readd it it will failed on windows) but it's useful :)
It's fun.

For sure there is a problem but not readding this file as it breaks compile on windows.

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_display(QWidget *parent)
{
    return new KNoteDisplayConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_collection(QWidget *parent)
{
    return new KNoteCollectionConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_editor(QWidget *parent)
{
    return new KNoteEditorConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_action(QWidget *parent)
{
    return new NoteShared::NoteActionConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_network(QWidget *parent)
{
    return new NoteShared::NoteNetworkConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_print(QWidget *parent)
{
    return new KNotePrintConfig(parent);
}
}

extern "C"
{
Q_DECL_EXPORT KCModule *create_knote_config_misc(QWidget *parent)
{
    return new KNoteMiscConfig(parent);
}
}

in KNoteConfigDialog.cpp
so --as-needed remove libknoteprivate but it needs for it.

I will move these line outside this file.

Is it possible to bring the versioning of KNotes in line with other KDE Applications?

(In reply to Justin Zobel from comment #12)
> Is it possible to bring the versioning of KNotes in line with other KDE
> Applications?

it will be release with 20.12.2

All good now, thanks for the quick fix

(In reply to Antonio Rojas from comment #14)
> All good now, thanks for the quick fix

Thanks for confirming it.
Regards

Great! That was fast! :D
Thanks guys! The menu works now, but, now that I am able to customize my new notes, I've noticed a "deadly" bug and an annoying bug. The deadly bug deleted my lonely note, or the contents in it actually, after turning the computer off and, the next day, on again, all I had there was just gone. The second bug, the annoying one, deletes the customized name for my note, kind of often.
The question here is, should I open a new bug report for each of those, or both (or more if I find more in the next few days) in one report?.
Cheers! :D

Yes, please report each remaining issue with a separate ticket.