Some time ago I posted about making 2019r1.1 work on newer versions of macOS
And there are reports that a related technique can be used to enable older versions as well (post copied here for posterity sake)
I ran into this problem today when I wanted to use an older version of Xojo (2018 R4) on Monterey. I found a simple solution that works at least for running the app from Xojo. I could not test if it also works for building Mac apps, because I don’t have a desktop license. Obviously, the better solution is probably to modify your code so that it runs with a more recent version of Xojo (and buy the Xojo upgrade if necessary).
- Run the Xojo app at least once, so that Gatekeeper is out of the way and you can modify Xojo.
- Right-click the Xojo app and choose “Show package contents”.
- Go to the folder Contents/Resources/SDKStubs/macosx10.14/System/Library/Frameworks/AppKit.framework
- Open the file AppKit.tbd with a text editor like BBEdit.
- Under “reexports”, you’ll find the problematic UIFoundation framework that’s referenced in the error message from the linker (/System/Library/PrivateFrameworks/UIFoundation.framework/Versions/A/UIFoundation).
- Simply remove this text (/System/Library…) and the preceding comma. Don’t delete the closing bracket, it should now be where the deleted comma used to be.
- Save the file.
Now Xojo will run your apps again.