New uNmINeD development snapshot is available for download!
Changes:
- Right click menu items now work in isometric mode
- Fixed isometric block rotation mismatches (mushroom blocks, logs)
- Fixed isometric tile rendering failures (broken in 0.20.4)
- Fixed isometric tile pixel alignment glitches (sometimes there was an one pixel gap between tiles)

Keen to testdrive this build, but the download page has not yet been updated..?
Thank you for reporting this. It should work now.
It is unfortunately still not working
What is your macOS version? Intel or Apple chip?