I tried that and it didn't work on my work ThinkPad (also those steps are dangerous it could brick your system if you so much as make a single mistake).
But that doesn't answer my question of why something as basic as Hibernate (copy RAM contents to HDD on power-OFF, then reverse on power-ON) isn't something that works out of the box on Linux distros, and instead requires 2h of tutorial reading and dangerous low-lvel tinkering for it to (maybe) work or brick your system if you mess it up.
> That doesn't happen under hibernate. You used sleep thinking it was hibernate, that's why you had that issue.
I mean, while asleep, the PC blinks its annoying light every second. While hibernating, it doesn't. I'm pretty sure there were no blinky lights, they would have prevented me from falling asleep. It's why I went out of my way to enable hibernating.
Also, see the other posts around the thread. There are absolutely ways to wake up a PC from hibernation. Even from full shutdown.
The Linux kernel disable hibernation when secure boot is enabled for security reasons (it enables the lockdown mode). I don't think it's especially an Ubuntu/distro problem. When secure boot is disabled, I think hibernation is supposed to work fine.
Apparently systemd supports building it now somehow (search for UKI, unified kernel image), but I'm too lazy to switch, since my current setup works great. But sooner or later I may be forced to, since my solution is apparently no longer maintained.
Basically, my distro will install the kernel, initrd and cpu microcode normally to /boot. But at the end of it, there's a hook being triggered, that calls sbupdate with stitches together the kernel, command line, initrd, and cpu microcode, signs it and dumps it in the /EFI partition as a single file. /boot is not a separate partition on my system, it lives inside the encrypted /. I also told my UEFI about this specific image using efibootmgr. This allows me to register the image as a bootable OS and use the UEFI's boot manager to choose between Linux and Windows on startup.
If you browse around that Arch Wiki page, they also tell you how to sign your own boot images. I've installed my own keys in the UEFI, since Arch's kernel isn't signed by anybody.
But that doesn't answer my question of why something as basic as Hibernate (copy RAM contents to HDD on power-OFF, then reverse on power-ON) isn't something that works out of the box on Linux distros, and instead requires 2h of tutorial reading and dangerous low-lvel tinkering for it to (maybe) work or brick your system if you mess it up.