Put the model under models\ultralytics\segm
Tested only on realistic wavy black hair. I don't think it will work on anime images.
The training was done a bit hastily, but it helps a lot to re-detail the hair, removing that initial plastic-like texture. It almost always identifies the clavicle area as hair as well, but this didn’t cause me any problems (it actually even helped).
Recommended: Denoise 0.4 and use the "Grow Mask" node with expand set to 15+.
The detection is "accurate" at finding hair, but unfortunately it leaks a bit onto the collarbone, and if you're wearing black clothes, well... it happens, right?!
Made to get by in a pinch, maybe they'll update to a much-improved version in the future.