I work at the Rubin Observatory and we're big into open source. We're thankfully highly encouraged to submit upstream, and we use lots of open source projects

I work at the Rubin Observatory and we're big into open source. We're thankfully highly encouraged to submit upstream, and we use lots of open source projects and try to fix them where we can. I don't know how to turn it into a fulltime career other than getting some kind of grant or working with a company to do it. Sponsorship sounds great, but probably requires some fame / traction, which is probably the hardest part, since you need the money to get the traction. Some open source projects also have foundations with employees or people doing contracts, like astropy (also driven with donations).