Hmh, I'm running Tumbleweed on a Ryzen 5 7600 and an AMD Rx 7800. Like you I don't fiddle with the defaults and this is my gaming rig (I'm working on starting just into Steam). I just have default KDE Plasma to launch Steam and play my games, I do my work on a Debian Trixie laptop. I have set up TW two years ago and only DUP-ed it since then. Actually, it is more stable then the Debian machine :o

I know, this is not helping you in any way. I only encountered weird instability with Linux when my RAM was not OK. Maybe check your RAM?