Can I import FLAC files into Apple Music in Sonoma on iMac 27?

Tim -

Music (and iTunes before it) has never had the ability to import or play FLAC. You can use a 3rd party converter to convert the FLAC files to a Music-compatible format such as ALAC, and import those into Music. I have used Switch for this purpose.

X Lossless Decoder, more commonly known as XLD, is the gold standard, and is free.