Hello,
OpenMandriva Lx version:
ROM 25.02
Desktop environment (KDE, LXQT…):
KDE
Description of the issue (screenshots if relevant):
Please help me with solving this, I don’t know exaclty when and why this has changed on my desktop, but it is very annoying:
Somehow even on dark breeze plasma theme those headers’ fonts are black, but should be white.
Switching themes, reset to defaults in plasma configuration tool doesn’t help.
Maybe leftovers from a custom theme.
Did you install kvantum?
Open systemsettings and check all the items.
You’ll need to logout/login.
Plasma cache also is often a factor. Try:
in console
rm -rf ~/.cache/plasma*
close console, start krunner and type
plasmashell --replace
I have done what you suggested, but it wasn’t successful.
I have also created a new user, log in to his session and there was a proper view with white labels, also a qt theme looks different than on my old user. So I have started to copy and overwrite ~/.config/ files related to KDE, plasma, QT etc from a new user home directory to the old one. Unfortunately it was not helpful either. Then I have remove everything from ~/.cache/ directory, but still themes mismatch occurs.
It must be related to some other files, maybe outside of user home folder, but related only to that user ? I have also noticed different qt layout, colors and checkboxes styles between those two users.
If we will not figure this out I will just do migration other files to a newly created user account and then remove the old one, but it would be nice to figure it out how plasma/qt is managing those styles.
If you did not heavily customize your desktop may be useful to remember what you installed.
Mine don’t look like that. Not accusing in any way, but something changed and it will be a lot easier to fix if you know what happened and maybe when?
Also, this is one of those times where it is a good thing to have a membership over at the KDE forums. It is their software and they have experts. Just sayin’. 
Yeah You are right, also backups etc. 
I remember 2 things that I changed recently, which could be related. Last ROME update with Plasma 6 bugfix version - but I have been updating also my virtual machine with OMLx ROME and that was fine.
Another thing was installing qt6ct package, running it and changing some fonts and styles inside - so this was probably causing this effect, maybe something was applied after a reboot and onbly then it was noticeable. So probably there is some bug related to using qt6ct and Plasma 6 Configuration Tool regarding styles, fonts or colors together which can break this.
As it must be something at user level, since with a new user is fine, you may try renaming your ~/.config directory (rename not delete so you have a backup).
I’d suggest to do it outside of plasma desktop after logout, like in failsafe xsession or so.
While at it. I’d also clear the plasma cache.
Reboot.
Postedit:
commands example:
mv /home/ruru/.config /home/ruru/.config-bak
mv /home/ruru/.cache /home/ruru/.cache-bak
Replace ruru with your username.
Yep, I have tried this too, but didn’t solve those… but going further I have started to review other config files in home directory and found this environment variable defined in .bashrc:
export QT_QPA_PLATFORMTHEME=qt6ct
removing this solved this issue! I am trying to figure out how it was added here. Maybe very long time ago and wasn’t doing anything because I didn’t have qt6ct installed before.
Thank You @rugyada for your patience and help!