What I don't understand is why there is so much resistance to the idea of having swap plus a separate hibernation file that is only enabled on demand. I finally got it working on my laptop, but it took a Lot of fiddly obscure manual configuration (which I wish I had documented - I don't just mean setting the offset in grub) and it still didn't play well with hybrid sleep, etc.

This is the only way to have hibernation that works at any memory pressure.