If beets doesn’t give the tag you want, you might have to start with metaflac (beets doesn’t grab every tag, because its upstream dependency mutagen doesn’t either)
Not exactly beets, although it would be cool to have this functionality in beets in the import / dupe detecting step.
I have files in beets and files elsewhere. With freezetag I can have two symlinks that only take up one file on my HDD. So I needed a hash based (not fingerprint based, not approximate) matcher.
I surprisingly couldn’t find one that operated on FLAC’s native MD5 hashes, built right into the tags.
I also learned about 1% of my files have a fake hash: 000000000000000000000000000…