Yeah, hibernate is weird on linux. Even after getting it working, there are a few warts with amdgpu for example.

I really appreciate distros that add an ext4 label to your root partition, so that you can just add resume=LABEL=Root to your kernel cmdline and get hibernation ready, nothing else needed. I do a custom arch install and make sure to do that. You can do it later from a live usb as well, iirc, e2label is the command.