I think @maxmueller50 probably put --node20 on his command line because that's what I suggested. (I have edited my post above to remove that CLI option)
I had previously suggested this for failure to install on a 32 bit Pi Zero, and it was marked as the solution.
Are you saying that the script gives no screen output whatsoever apart from that error message?
And that the file /var/log/nodered-install.log does not exist?
Precisely which version of RPiOS did you install on the Pi?