Then, re-enabled Wayland with NVIDIA purged, and suspend works there.
Then, re-installed and reenabled NVIDIA 510 (which blakclists Wayland and puts me in X11 since no Wayland support yet), and boom problem is back exactly as before, same nv_* traces and ACPI errors (I didn't see the ACPI errors when I had disabled NVIDIA, so it looks like it is causing those as well).
So 100% certain now that the bug is in NVIDIA drivers.
Then, re-enabled Wayland with NVIDIA purged, and suspend works there.
Then, re-installed and reenabled NVIDIA 510 (which blakclists Wayland and puts me in X11 since no Wayland support yet), and boom problem is back exactly as before, same nv_* traces and ACPI errors (I didn't see the ACPI errors when I had disabled NVIDIA, so it looks like it is causing those as well).
So 100% certain now that the bug is in NVIDIA drivers.