[later edit]

is not a valid LUKS device".

"Then, find /etc/fstab on the [encrypted/decrypted] drive, remove any lines with

and unmount and reboot"

You have progressed beyond .."Device /dev/sda1So now you can revisit this thread ..one writer suggests .../dev/mapper/ubuntu--vg-swap_1But first ..the existing /etc/fstab or you may not be able to boot up again without restoring it.