I also came here to suggest Indie Hackers. I haven't been active there for a while, but it's probably the best online community I know for solo founders looking

I also came here to suggest Indie Hackers. I haven't been active there for a while, but it's probably the best online community I know for solo founders looking to bootstrap a company. It might not be exactly what OP was looking though given the community is fairly focused around tech startups.