I'm on X and every time I launch a game I haven't played in a while, there's a high chance that it will have low FPS, stutter or just straight up won't work anymore. This isn't about starfield, it happens with every single game I play. Titanfall 2 is a recent example. It runs better on my steam deck than it does on my PC with a 1070 Ti. It used to run well about a year ago.

If the proton version didn't change, the issue is always the nvidia driver. But since I don't know when it broke, I have to try a few different versions to find one that works well with that game, which might break others.

It was a similar story on windows, I used to just not update the driver unless I absolutely had to.

It's been a while since I had an AMD card, but there was only one time when I saw a driver regression and my friends with AMD cards also don't have any issues. They're on windows, but I assume that this aspect transfers to linux with AMD just like it does for nvidia.