When I switched to Linux (because the Mac was old enough not to get updates from Apple), the thing I missed most was support for the external Magic Trackpad (the first version with the removable batteries). I searched around and found some solutions, but they were all outdated and/or abandoned, and none of them could get me all the features and gestures that Apple supported natively since about 8-9 years ago.

Though Linux drivers have improved a lot over time, there are still some areas like this that don't get attention. Not that there isn't a large enough user base, but for many other reasons. I would gladly support a crowd funded project by reliable people on such things.