> Other data sources such as the MP3.com rescue barge, PureVolume archive, and Anna's Spotify archive lack the country-of-origin metadata, so are of less interest to me. It may be possible to use an LLM to guess the language of each track title, but someone else will have to do that.

I would guess that combining these sources, along with info from MusicBrainz, would help quite a bit? Still, I'm rather surprised Spotify doesn't provide more information about artists.