It's not a cardinal sin, it's called being a brave pioneer :)
Anyway, fwiw I've noticed something similar where steam just (re)starts all of a sudden while playing. Like I notice the game gets sluggish, then focus changes to the steam client, complete with the "new offerings" sale popup that comes when starting steam. And I did have steam overlay UI freeze completely recently but restarting the game and steam fixed it.
Kubuntu 22.04, X11, nVidia 3060 with 525 driver