I am not sure if we are discussing hibernation for encrypted systems only, and I do not know what special provisions are needed for that, but for anyone curious, here is what I do on my own machine (not encrypted) per my own notes for setting up Arch, with a swap file rather than a swap partition, and rEFInd as the boot manager (the same kernel params could probably be used in Grub too, though):

• create a file at sudo nano /etc/tmpfiles.d/hibernation_image_size.conf (copy paste the template from https://wiki.archlinux.org/title/Power_management/Suspend_and_hibernate)
• if you made your swap file large enough (~1.2x ram size or greater), set the argument value to your amount of ram, e.g. 32GB= 34359738368
• after a reboot, you can verify this with cat /sys/power/image_size
• findmnt -no UUID -T /swapfile to get swapfile UUID
• filefrag -v /swapfile | awk '$1=="0:" {print substr($4, 1, length($4)-2)}' to get offset
• Go into your kernel parameters and add resume=UUID=### resume_offset=###
• e.g. in /boot/refind_linux.conf (with efi partition unmounted)
• go into /etc/mkinitcpio.conf and add “resume” after the “filesystem” and before the “fsck” hooks
• run mkinitcpio -p linux-zen (or equivalent linux type)---