However my device wasn’t encrypted. However near the bottom are instructions if you are and they don’t quite match what you said you did. Maybe give it a try?
“Encrypted installs In case /dev/sda2 is the encrypted root partition you need to unlock:
sudo cryptsetup open /dev/sda2 mycryptdevice
It will ask for your LUKS passphrase and unlocks the device into the path /dev/mapper/mycryptdevice
This path can be used to mount the device:
sudo mount /dev/mapper/mycryptdevice /mnt
Followed by mounting the ESP (EFI-System-Partition) into the already mounted system:
sudo mount /dev/sdXn /mnt/efi
where in all cases /dev/sdXn needs to be changed according to what is used on your install as partition/device path and the mount path for the ESP needs to get changed according to your installed system in case. If it is /efi you need to mount on /mnt/efi if it is /boot/efi it would be /mnt/boot/efi …”