Using Solus Plasma with Nvidia RTX2060. Been on it as my daily driver since the offical ISO released.
The only lockup/freezes I have experienced are:
Brave Browser - when streaming Youtube only.. Sometimes it just hard locks and that's it. I am 99.9% sure it's Brave's fault. They'll update, then it will be fine for a month, then after another update it will do it again...
Feral's gamemode. Sometimes when using gamemode, the game will hard lock the system. I'll remove gamemode from the Steam command and the game will run for hours. Re-enable, hard lock. Again 99.9% sure this is an issue with gamemode.
I've been using sysrq (REISUB) to reboot safely when it happens, although I'm still looking for the correct Solus way to implement this permanently.