Comment 17 for bug 1802617

First, besides the active swapfile, that caused the trouble, I found an additional uncommented line in my fstab, referencing /dev/mapper/yoga--vg-swap_1. Whether this was used before or is just a relict I cannot tell.

So I went with /dev/mapper/cryptswap1, which was active; also checked that the device really exists in /dev/mapper.

To not lose encrypted swap, I followed the advice from #10:
* uncommented swap in /etc/fstab and /etc/crypttab
* rebooted
* restored the uncommented lines
* update-initramfs -c
* update-grub

After this I could reboot without issues.