Since some time baloosearch spits almost only empty strings as results,
(I reported it somewhere here, was supposed to be fixed by 5.15, but weren't)
I tried adding $HOME to exclude folders but it turns out that this option is ignored.

cat ./.config/baloofilerc:
[Basic Settings]
Indexing-Enabled=true

[General]
dbVersion=2
exclude filters=*.nvram,CMakeTmp,confstat,CVS,*.loT,*.m4,config.status,.xsession-errors*,*.rcore,*.pc,lzo,litmain.sh,*.pyc,*.la,cmake_install.cmake,*.tmp,ui_*.h,CMakeTmpQmake,.git,*.class,Makefile.am,*.po,*.o,CMakeCache.txt,*.swap,.svn,*~,core-dumps,*.omf,.bzr,.hg,.pch,*.elc,*.lo,CTestTestfile.cmake,po,*.aux,*.moc,*.orig,.obj,_darcs,confdefs.h,__pycache__,*.part,*.rej,*.gmo,libtool,conftest,CMakeFiles,.uic,autom4te,moc_*.cpp,.moc,qrc_*.cpp,.histfile.*,*.vm*,*.csproj,lost+found
exclude filters version=2
exclude folders[$e]=$HOME/
first run=false
only basic indexing=true

Reproducible: Always

Steps to Reproduce:
1. balooctl disable
2. edit add home to exclude folders (in UI or directly to baloofilerc)
3. balooctl enable

Actual Results:  
(balooctl status)
Baloo File Indexer is running
Indexer state: Idle
Indexed 70373 / 70373 files
Current size of index is 39.93 MiB

Expected Results:  
most files have status: Scheduled;
some actually turn in the search results

kf-5.21
(the fact that in the bugzilla You can only select 5.20 is strange... 
does it mean that "kde is dying" ;-)??

this is i686, i.e. 32-bit installation. I have none of these problems on 64-bits installations I own