The package maintainer of LilyGlyphs has ported his Python 2 scripts to Python 3 (see
https://ctan.org/pkg/lilyglyphs?lang=en) and thus is eligible to be re-included in the texlive-music package on the Debian repositories. Looking through the changelog, the Python 2 scripts were the reason LilyGlyphs was removed from the distribution, so this should fix that dependency issue. See commit history at
https://github.com/uliska/lilyglyphs for details if necessary.