(sorry if this is the wrong place, Krita's Contact page doesn't really tell where to report bugs)

The download page for the OSX version says "Minimum version of OSX 10.9 required." Actually, the minimum is 10.11 (I found out the hard way, since I have 10.10 )

No, that's not correct. I test the app bundle I make on 10.9, and there it works. For some reason possibly only Apple can fathom, you can make a build on 10.11, have it work on 10.9 but not on 10.10.

The problem is actually much more complicated. We have 10.9 and 10.11 devices. We test the dmg on both. For mysterious reasons, we have both people reporting it IS working on 10.10 and people reporting it ISN'T working on 10.10. Right now, our best guess is that it might be a case of OSX devices with AMD cpu/gpus instead of Intel ones where the dmg doesn't work.

If that's the case, I am guessing you have an AMD Mac device?