I was interested in a startup in the cassette industry - No major research or anything, just a weekend idea I had once upon a time. Where does one find and market to the cassette fanbase?
1. The ambient scene: http://fangsandarrows.com/ was a great community, similar to HN crowd. Serious people. Not sure if it's down for good, here's their bandcamp: https://fangsandarrows.bandcamp.com/
2. Vaporwave: If you don't know it: https://en.wikipedia.org/wiki/Vaporwave here's a label https://dreamcatalogue.bandcamp.com/
3. Post-punk / post rock / synth pop (the dark stuff like John Maus) etc. Concrete basement shows etc.
https://opaltapes.bandcamp.com/ is a great label (I really like Huerco S. and Basic House)
What's your email address? Email me first if you prefer to stay anonymous - My email is in my profile :)