I noticed there was a thread about performance in some games in which people had been able to restore performance by reverting to a previous kernel version. However, before I could try that a new minor update came out, and after applying, her computer started running Noita fine. To my eyes still seems like it has minor hitches, but they are more like an occasional micro stutter instead of multiple seconds of half frame rate.
Worth noting that my main gaming rig ran Noita just fine the entire time. It appears to have been a very specific combo of her hardware and a kernel (and associated drivers) version.
Tangentially, I have been playing through Half-Life 2 on my main gaming rig, and was having an issue with the game suddenly becoming extremely choppy after an hour or so of gaming. Like single digit frame rate. The latest kernel update appears to have mitigated that issue as well, but I did change some other settings as well so I can’t be sure.