> the song commonly known as “願榮光歸香港” or “Glory to Hong Kong”

I'd never heard of it until now.

> the Song first emerged in August 2019 in the form of a video publicly accessible on a channel “Dgx Music” on the YouTube. The composer of the Song used a pseudonym “Thomas dgx yhl”

OK, so here are multiple versions of the song: https://www.youtube.com/@Dgxmusic

EDIT: Great job, Google, I see where you stand. The first song is blocked: "Sign in to confirm your age. This video may be inappropriate for some users." Yeah no.