Comment by reidrac
It can be done; an example is Igalia: https://www.igalia.com/jobs/
> We are a worker-owned, employee-run company with more than 20 years of experience building open source software in a wide range of exciting fields.
If there's enough money to go to the developers actively working on a product to make it sustainable, I think a lot of people would get on board with that and would pay for FF.
> If there's enough money to go to the developers actively working on a product to make it sustainable
That's a big if. AFAIK most open source project developers don't get remotely enough donations to support them working on it full-time. The ones that do are the exception, not the norm.