I have finally decided that OS X Catalina is the end of the line for OS X support by UECIDE.
Versions of OS X after Catalina (10.15) will no longer be supported
This is because Apple's requirement that all software be "notorized", which will be enforced with the next version, makes it almost impossible to distribute software that has not been developed in XCode.
That's not to say that I won't be producing OS X packages any more, but running them on anything after Catalina is not something I will be able to either condone or assist with. Especially since so much is already broken in Catalina that trying to massage UECIDE to work is becoming harder and harder.
If you want to run UECIDE on OS X newer that Catalina (and even on Catalina to be honest) I would recommend using some virtualisation software to create a virtual Linux machine and run UECIDE within that.