I know it's probably not practical to monetize an open source programming language, and they don't centrally manage it, but that seems to be their big differentiator and contribution to the software world as of 2020, as far as I can tell. They were pioneering back when they were driving a lot of the evolution of browsers and web APIs, and providing a way less awful alternative to IE, but by 2020 Google's basically upstaged them in all those areas, and I don't see that trend ever reversing at this point. But Rust might live on in a big or huge way, possibly even long past their solvency as an organization.
So I don't know exactly what I'm trying to say with this post, and I don't know how it could help them financially, but maybe leaning into Rust or other similar very ambitious attempts at fundamentally shifting the software ecosystem could let them remain if not successful, at least relevant and acclaimed. Maybe Servo could've been one of those, but it seems like vaporware at this point (besides the parts Firefox cannibalized, like Stylo).
"Nobody pays for a browser", they say. Well, they might pay to see some features in!
A long time ago firefox(program) started asking for donations. I've donated 5$(I was a poor student in Poland[1]). After the donation, I found out that money will not be used for FF development (why firefox page did not mention that?). Long story short it was my last donation to them.
[1] Now I'm not a student ;)