My experience with 3.5.1 and newer is that a few games crash/closes down after a few minutes of gameplay but that not all games does it. I have personally locked my deck to 3.4.11 until stuff works properly on the “Stable” release.

One thing you could try is running games in Desktop Mode and see if they work there. I also think you should consider speaking with Steam Support if the issues continues for you.

Do all games crash?

Do they run at all or do they crash instantly?

If they all crash try restarting or switching proton versions but consider doing an RMA if none of it works. If only some games crash then you could have been cursed by the new 3.5.5 Stable OS which has broken some games for me atleast.