I’m assuming it’s mp3. As far as I know the lossless versions of TROS have never been shared online.
Yep, that is correct. Just from what I found on my search, it seems that for all of the ST FYC soundtracks that were posted online on Disney’s FYC site, they were only uploaded as mp3 files (160 kbps for TFA, and 192 kbps for TLJ and TROS).