Wikipedia has an unusually high hit rate for me. I start reading about a band, a genre, or something music-related, then before I know it, the wiki rabbit hole of blue links has introduced me to 50 other bands. Some of my favourite bands were found this way. If you're averse to using anything web-based at all, maybe you could get your hands on a music encyclopaedia from the library or something. If you're into a specific genre, you can probably narrow down the scope with a book just about that genre.
I have never, not once in my entire life, been recommended an artist by an algorithm that I ended up liking. Not on Spotify, not on Last.fm, not on Bandcamp, it just doesn't happen for me π€·β