Hmmmm…Navidrome has supported lyrics for a while now, no? Apps like Feishin will fetch lyrics for you based on the song being played, if it’s available that is. But it doesn’t embed them, to my knowledge. However, since I still have a stripped down Windows 10 installation, I used MusicBee to embed the lyrics. Highlight the library, and let it eat. If your library is large, it will take some time. When finished, the lyrics will be embedded in the audio file, and will display in Feishin and in Navidrome.

I know that beets has a lyric plugin, and that might be an avenue for you OP. However, in my case, I started with MusicBee so very long ago, and it’s still a top notch player imho, even tho it is a Windows app.