It supports ALAC.

There’s a handy app called XLD (X Lossless Decoder) that will convert from FLAC to ALAC (and probably back) in a couple clicks if you need it. Lossless means I don’t really need to care whether my music is in an equivalent format, but I will admit it’s a bit silly.

https://tmkk.undo.jp/xld/index_e.html

Broken on purpose in this case, I am sure, for the same reason Spotify doesn't deal with FLAC.