Consider ffmpeg. You can donate via https://www.ffmpeg.org/spi.html
How much money do they make from donations? I don't know but "In practice we frequently payed for travel and hardware."
Translation: nothing at all.
If such a fundamental project that is a revenue driver for so many companies, including midas-level rich companies like Google, can't even pay decent salaries for core devs from donations, then open source model doesn't work in terms of funding the work even at the smallest possible levels of "pay a reasonable market rate for devs".
You either get people who just work for free or businesses built around free work by providing something in addition to free software (which is hard to pull off, as we've seen with Bun and Astral and Deno and Node).
There are examples of foundations or other similar entities paying developers, like Linux, SQLite, even Zig.
Maybe the difference is some projects rely on core contributors more because external contributions are more restricted in some way.
But sure, the entire open source model doesn't work, lol