I don't know for sure it's a steam issue, but in the last few days my bluetooth controller (xb elite 2) has been very inconsistent about connecting to steam and any games launched from steam. jstest doesn't see any problem, but often Steam's Test Device Inputs won't get anything from it, or if it does, the game might not. One day it'll work, the next it won't without me having changed anything 🤷. Plugging in over USB gets rid of all issues.
Also, the new big picture mode on nvidia is very low framerate. Sub 10fps. It's not great.