https://bugs.freedesktop.org/show_bug.cgi?id=107947
--- Comment #6 from Kent Ross root.main@gmail.com --- Good-citizen update for you: I have resolved my immediate problem. These apparent crashes are still happening pretty often when display modes change, but do not seem to be the root cause of my issue.
(In summary: my AMD and nvidia GPUs were in slots 1 and 4 of my motherboard; I moved them to slots 3 and 1 respectively, which gives both of them full x16 lanes instead of both being on x8 lanes if the documentation tells the truth, and while the system still shows bios and grub on the nvidia card, booting and resuming in ubuntu now seems to work fine. Quite unsure why, but there you have it.)
Apologies for any unhelpful noise, good luck with whatever this bug actually is, and thank you for your work.