You’ll also need to modify the kernel parameters/initramfs configuration to add the resume parameters in the right spots, or the system will hibernate but not try to resume your session on boot.

In the right spots? I was in the impression you only need to do that so one place, in the bootloader’s boot entry (or, yeah, if there are multiple entries then possibly each one). Which other places should I also look?

Also, I’ve recently set up hibernateion for someone, and IIRC forgetting the resume= kernel parameter is not that critical today because it will immediately resume instead of completing shutdown.