Tsm for the answer (sorry for the delay, I was in a traffic jam, jk). At the end I gived up and ended redownloading my whole playlist in m4a with yt-dlp and directly with the metadata, so I saved a lot of times and a lot of problems haha

You might want to check this out too:

beets: music library manager and MusicBrainz tagger. It has a dozen more other features.

Unless something has changed recently, MusicBrainz Picard is my go-to, and what I usually see recommended.

Don't think it has webm or mp4 support. I might be wrong on that though. My collection is mostly flac, mp3, m4a, and the occasional ancient wma I've carried forward since high school.