Maybe not for your exact use-case. But "open" doesn't need large numbers, market saturation or a monopoly: those are traits that come from investor-fueled business-models.

A mastodon account that has great communication with seven other accounts is a 100% success! It doesn't need access to billions of people, it just needs to fulfill a need: talk to several fine people. And it often does this just fine with a very small social graph, even.

A musician doesn't need a million streams, they need enough revenue to be an income. On spotify (or youtube, etc.) that, indeed, means "millions of streams". But it could just as well be five tshirts sold, twenty-eight .zip files @ €9.88 sold, and three vinyl shipped in a month.

The "numbers" that mark "competing with" faang, really don't matter. We don't need to make billions, we just need to make a good income.