https://askubuntu.com/questions/1240123/how-to-enable-hibernate-option-in-ubuntu-20-04

sudo apt install pm-utils hibernate

cat /sys/power/state

should return freeze mem disk

Get swap UUID

grep swap /etc/fstab

Enable option in GRUB; edit /etc/default/grub. Change

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash resume=UUID=YOUR_VALUE"

Then

sudo update-grub
sudo systemctl hibernate