Also very curious about this. I went to his websites with the goal of finding out how I could give him money. It was incredibly difficult for Visa List - and all I got to was a buymeacoffee page that couldn't possibly be the only source of income. If OP is making money off of these from users then they could make way more by having an obvious CTA in the nav to give him money.
Its different for different for different microstartup. Everything i did is through organic channels for Visa List it SEO for Apps its ASO. Once i got the users, it was easy to tweak and optimise revenue generation.
I see a potential problem, see if I can solve it. See if it's already being solved, if not I pitch the idea to few people. If atleast 50% got excited. I pick this idea to build.