After a week or so of normal use (with kernel 6.0.0-6, from backports), the system seems to work just great. Very responsive, I noticed no crashes or lockups whatsoever.
My only concern currently is that in suspend mode the laptop discharges much faster than I would have expected based on my former laptops. But I have yet to do a serious comparison with what other people posted ( e.g. Suspend on linux drains a lot of battery compared to other laptop - #26 by Matt_Hartley , Test results for standby battery use of Expansion Cards ) in order to find out if the OS is somehow to blame (or maybe the expansion cards). I will maybe do a test of Ubuntu 22.04 to see if it fares better.
By the way, the only other very minor annoyance I had was the somehow distracting automatic brightness regulation, but it can be easily disabled: "auto-brightness" aka ambient light sensor in Linux? Details? - #5 by devnull