You can adjust the renderer settings by typing plasma renderer into Krunner (which is opened with the Alt+Space shortcut).
Alternatively, you can open the renderer settings from the command line:
kcmshell6 kcm_qtquicksettings
The settings should be “Automatic” for the rendering backend & render loop, and leave “force” unchecked for GL Core Profile.
Reference:
Regarding using AI:
The first place Manjaro users should go to for advice when they experience issues with their system is the Manjaro Linux Forum. AI is just a high-end text predictor, and is usually trained on data that is at least a year old. As Manjaro is a frequently-updated rolling release, any advice from an AI LLM will almost certainly be out-of-date.
And you are correct - there were some very big changes last year, especially for Plasma (the Plasma 5 → Plasma 6 update).