raxod502 Okay, I disabled developer options, and I still see that apps are very quickly killed on GrapheneOS. For example I can switch away from Firefox to another app for less than 30 seconds, and when I switch back, it's been killed and has to reload whatever was open from scratch. The same is true for every other app I run. The only safety is that whatever's in the foreground is left alone.
Hmm, that sounds almost exactly like the behaviour that is triggered when enabling the developer option "Don't keep activities". Did you reboot your device after having disabled developer options? If yes, what happens if you enable developer options, enable and then disable the "Don't keep activities" setting, then disable developer options as a whole and reboot your device?
(I admit that sounds a bit like fumbling around in the dark, but it would take less time to give it a try compared to factory resetting).
If that doesn't improve things, I'm curious to know if the problem can be reproduced in a freshly created secondary profile.
raxod502 This behavior is a bug, right? Is disabling developer options a workaround for the bug? If so, why?
I don't think anyone here is yet able to determine the specific cause of the malbehaviour, so the most productive approach might be to try the various options suggested. Although I disagree that a factory reset is one of the first options to attempt in this case, because of the pain resulting from time spent (although I suspect it would solve the problem, but without immediately identifying if it is caused by a user configuration; so you might be correct in that the issue would reoccur at some point. On the other hand, a factory reset could make it easier to retrace what you might've changed (in terms of settings) immediately prior to the issue reoccuring).