If you don’t use Cinnamon anymore you might clean your system of it. With it I think Kvantum is also not needed anymore and that removes also all Kv Themes. I don’t have it installed on Plasma. It’s all up to you how you want to proceed with it.
You can also check the same env in (systemwide vs. user-specific)
cat ~/.profile
Regarding Anki, I just installed it and can confirm the dark font on dark background.
However, change in Anki Menu > Tools > Preferences > Basic > Theme: Dark and it has a dark theme. It runs on Qt6 so the looks is slightly different, well because of Qt6.
For other applications please also check in application preferences whether you have an option to set a different theme.
Anki started in terminal:
anki ✔ 1m 38s
Running with temporary Qt5 compatibility shims.
Run with DISABLE_QT5_COMPAT=1 to confirm compatibility with Qt6.
Preparing to run...
Qt warning: OpenType support missing for "Noto Sans", script 15
Qt info:
GL Type: desktop
Surface Type: OpenGL
Surface Profile: NoProfile
Surface Version: 3.1
QSG RHI Backend: OpenGL
Using Supported QSG Backend: yes
Using Software Dynamic GL: no
Using Multithreaded OpenGL: yes
Init Parameters:
* application-name Anki
* browser-subprocess-path /usr/lib/qt6/QtWebEngineProcess
* disable-features ConsolidatedMovementXY,InstalledApp,BackgroundFetch,WebOTP,WebPayments,WebUSB,PictureInPicture
* disable-setuid-sandbox
* disable-speech-api
* enable-features NetworkServiceInProcess,TracingServiceInProcess
* enable-threaded-compositing
* in-process-gpu
* use-gl desktop