My plugins seem to work fine display-wise and sound-wise
Big Sur 11.4
Serum synth
Sylenth Synth
FabFilter any plugin
Native Instruments (just little use not too sure, battery is working fine)
iZotope Suite - tested most of them, I guess the Iris synth is still not supported
Output any VST - Portal, Thermal, Movement (Kontakt instruments not tested yet)
NUGEN - mastering tools
MAAT TP meter and corellation
XLN XO - the best VST plugin ever!!!
Lexicon native bundle
SSL compressor
WAVES various plugins (seem to work fine)
Soundtoys (several tools, i.e. FilterFreak, Decapitator, AlterBoy)
However, it seems like Reaper is frequently crashing when loading a project. Once it is loaded all VSTs work fine. The problem only arises on load.
I can not tell which plugin is causing this...
When I start Reaper without any project it loads fine. So it looks like some VST is causing trouble.