I used to hang out at Head-Fi a lot in the early ‘00s. It’s a headphone and headphone accessories (amplifiers, DACs, etc.) forum, and people nerd out about building their own stuff. I recall writing a review on some obscure Chinese brand of sound card that people liked, because it happened to have a really good DAC for the rear output (it was a surround sound card, back when that was something interesting).

I gradually lost interest when they started heavily pushing commercial sponsors. I get it; sites aren’t free to host, and moderator time isn’t free / unlimited, but it’s still sad.

Sites are surprisingly cheap to run all things considered - I remember asking the owner of an fairly prominent aerospace enthusiast forum (one of the biggest on the internet) how much he spends on hosting - he told me he hosts on a Linux box on DigitalOcean that runs phpBB, and he spends about $50/month for the whole website - not a crazy amount even for a hobbyist.

Bodybuilding.com's misc board was essentially the same sort of raunchy teen hangout as /b/, sans the porn. It wasn't anything goes, but a lot did, and of course you were dealing with the kinds of meatheads (said lovingly) who would happen upon bb.com in the first place.