Everyone should copy thunderbird's donation model
Traditionally with FOSS software like this, the donation campaigns happen through social media, project blogs or mailing lists. That's nice and all but it has the major flaw that it only works for a specific group of people...
So the change was quite simple: Ask users directly in the software, once a year in december.
The second they implemented this change, as visible in their 2022 Financial Report their user donations more than doubled; Going from ~2.5 Million EUR to ~6.4 Million EUR. And across all sources of income Thunderbird has, user donations are by far the most prominent, making up (as per their own words) 99,9% of all income to the project.
People are willing to fund open source development, but don't know how and there isn't any expectation that they will. When we figure out patterns like this that work, we should spread them around.
Obviously this doesn't work for every piece of software - imagine if grep did this - but it's a tool in the toolbox.