I had the same error trying to boot an encrypted system & followed the steps to reinstall Grub. Unfortunately, now I am just in some weird loop where it keeps taking me to the boot menu where all I can do is select my main SSD & it starts all over again.
I am trying to find a solution online but finding it very confusing. I think I need to some how mount my encrypted disk & chroot into it. I’m lost currently! I do have a Timeshift restore point but don’t know how to get to it.
Thanks, Ruziel 