Maybe but I've reached out to open source maintainers to offer them contracting work focused on their library and they have pretty much unanimously replied that

Maybe but I've reached out to open source maintainers to offer them contracting work focused on their library and they have pretty much unanimously replied that they are too busy. And we were willing to pay above market rates to work on a product that has a significant global user base. There's definitely culture, process & funding problems around open source but for the most part being an open source maintainer seems like it's very good for your career. I suspect being an open source project maintainer is a self selecting grind.