The only thing I can find is for Gimp 2.10 Gimp 3.0 is obviously very new.
https://www.gimp-forum.net/Thread-GMIC-i...-13-worked
and
https://ports.macports.org/port/gmic-gimp/
...but someone with less success
https://discuss.pixls.us/t/gmic-qt-for-g...ma/39936/6
Very-very few MacOS users visit this site. I advise asking the same question on pixls.us amd possibly gimpchat.com
https://www.gimp-forum.net/Thread-GMIC-i...-13-worked
and
https://ports.macports.org/port/gmic-gimp/
...but someone with less success
https://discuss.pixls.us/t/gmic-qt-for-g...ma/39936/6
Very-very few MacOS users visit this site. I advise asking the same question on pixls.us amd possibly gimpchat.com