I run https://keygen.sh. I don't share revenue figures anymore, but it does well these days. Profitable since year 1. I'm still the sole employee at the company (although I currently have a couple firms/consultants helping me push a handful of projects forward right now), but I'm evaluating this year whether or not I want to continue going solo.

Do you have questions about running a one-person SaaS, or are you just looking for link dumps? I'd prefer the former tbh.