Hi Japhy,
It appears using an older system wasn’t necessary. I was lucky to find a Time Machine backup from last december with the Monterey system on which rhino 5.5.5 still works.
To be honest, for me it would have been more helpful, if McNeel could more precisely describe which (preference, caching, plist, etc) files in the system needed to be placed back after using the online rhino 5.5.5. installer and not immediately refer to the list of recommended systems.
Is that the issue though? Updating MacOS is going to break the legacy versions a variety of ways, hence not supported (no more revisions to Rhino Mac 5.x).
Great to hear you got it going and that its working for you.
What MacOS was successful (in case others want to know)?
The strange is that de installer didn’t seem to work but the version that’s been on my computer since 2015 - that I now placed back via a time machine backup - does. That’s why I felt it was strange that it didn’t work anymore after I reinstalled it via the online installer at rhino3d.com
The system it’s now on is macOS Monterey version 12.7.4