Comment # 12 on bug 1197558 from Takashi Iwai

And, let's check with nomodeset boot option.  This will boot without the native
graphics (amdgpu), driving with EFI framebuffer.  It might be that it won't
reach to the graphics environment, but it's fine with Linux console.  There you
can run manually like "systemctl suspend".

At resume, you'll likely lose the graphics screen, but the system should still
live.  You can type blindly or reach via network there.  e.g. run a command
(e.g. "systemctl suspend" again) and see whether it works as expected.

If the suspend/resume works without graphics, it's narrowed to be a problem of
amdgpu.  If it still hangs up, it's something else.