I'm doing pretty well selling a WordPress plugin, https://mediacloud.press/
It's an equal mix of rewarding and frustrating. It's a lot more work than you'd expect and now I've a deep understanding of why support tools are as obtuse as they are.
It's generating enough income that's livable and freeing me up to focus on other related projects. I'm going to be launching a SAAS version of the plugin later this year.