Sad days.
I was just coming back to say I found and wrangled the bug.
(simply was the first getopts loop interpreting the long option, which it does not support)
Its fixed and updated for the future though. So thats something.
I am not sure what your exact error there is.
I suppose we hope it can be accessible via a “Fallback” boot option or … at the very least a Live ISO and a chroot (or manjaro-chroot).