Scroll used to basically do this, but then it was acquired by Twitter, lobotomized, and turned into a Twitter Blue feature. After that I gave up on it.

Honestly, I think a service like Kagi (together with their Orion browser) would be best suited to set up a service like this. I've been thinking for some time about exactly the idea you're proposing.

The interface could be so simple: a button in your browser you click to donate to the current open tab. That button turns into a pay button if you've opened a page that demands payment. And the page could specify how much it costs.

We would love to do this, and we are waiting for the right technology to do so!

I'd use a service like that as long as this removes all advertising and third-party analytics from the site as well.

Payments online are a giant nightmare pit because the US finance world is very very scared of sex work. As long as that doesn't get solved, I don't see easily accessible and distributed payments working in a way that doesn't involve hoops most folks don't want to jump through (i.e. sending in ID to some corp that will definitely leak it a week later or cryptocurrency).