Versions:
     Linux: 4.3.6-0+deb11u1
     Windows: 5.1.2-full_build-www.gyan.dev

The 'tmpo' metadata tag within a .m4a audio file is not recognized by
ffmpeg and is never processed or output.   Neither the command line
interface nor the api returns this tag.

References:
https://picard-docs.musicbrainz.org/en/appendices/tag_mapping.html
(under BPM)

Apologies if this has already been fixed.