Edit: Just checked Homebrew analytics. >10k recorded installs in the past year (low single digit number of releases during that period, no major publicity event). I don't have readily available analytics for other installation channels on macOS, or analytics for Linux and Windows which are pretty fractured. Point is the user base is sizable.
I can't remember ever hearing someone talk about how successful their donation button was. I can remember plenty of people describing how few people ever click it, though...
My own personal donation methods total $15 from one person in the past 5 years since we forked the project and started maintaining it. We have more users than many start ups do and I know that there are several companies using our software.
[1]: https://github.com/streamlink/streamlink [2]: https://opencollective.com/streamlink