If you removed Quartz, there would be no GUI left.
If that's what you want, then there is Darwin out there.
https://github.com/apple/darwin-xnu
There have been various efforts to make it run as a standalone OS with X11:
• Pure Darwin: http://www.puredarwin.org/
• Open Darwin: https://archiveos.org/opendarwin/
• Next BSD: https://github.com/NextBSD/NextBSD
But they aren't much use.
If you just want tiling windows, then I use Rectangle:
https://rectangleapp.com/
For me that replaced Spectacle when that was discontinued:
https://www.spectacleapp.com/
If you removed Quartz, there would be no GUI left.
If that's what you want, then there is Darwin out there.
https://github.com/apple/darwin-xnu
There have been various efforts to make it run as a standalone OS with X11:
• Pure Darwin: http://www.puredarwin.org/
• Open Darwin: https://archiveos.org/opendarwin/
• Next BSD: https://github.com/NextBSD/NextBSD
But they aren't much use.
If you just want tiling windows, then I use Rectangle:
https://rectangleapp.com/
For me that replaced Spectacle when that was discontinued:
https://www.spectacleapp.com/