I was trying to use the new hair feature of Blender 3.3.
I duplicated and separated the scalp of my model (⇧ ShiftD > P) and then added the Empty Hair object.
When I tried adding hair in Sculpt mode, I got the error
Missing UV map for attaching curves on original surface, so I added a UV map named "UVMap".
I tried adding hair again, and now I have the error
Invalid UV map: UV islands must not overlap.
I've tried unwrapping the UV map, but no luck there either...