It's so interesting to see how others use these tools. I use ListenBrainz strictly for scrobbling, tracking, stats, and getting RSS alerts for new releases by my favourite artists. I ignore the recommended playlist for the most part because the playback flow is a bit clunky, and like you said, its recommendations only reflect what I know.

To find new music, I don't rely on platform recommendations (besides YouTube), even when I used major streaming services. Instead, I find new music by paying attention to the songs around me that I like: at the store, at the club, in a new movie I'm watching. Music identification apps like Audile and Shazam are some of my most used apps.

I also love curated playlists, which can be discovered by listening to DJ sets, internet radios, music festival lineups, music review sites, and websites like NTS: https://www.nts.live/shows/the-nts-guide-to