I am no FOSS expert, but I think a project could sell the binaries as downloads on their website and still make the source code available via a github or something. You don't have to produce binaries for people to be FOSS (I don't think).

I wouldn't mind seeing a world where wallet projects charge by release, say something like 5000 sats to download the latest version's binaries. If you want to compile from source, you can do that, but if you want it nice and easy pay for the release.

You don't necessarily have to upgrade if you're running a prior release (although the problem becomes vulnerabilities...) and maybe the project makes old binaries available for free. I haven't thought this model through well enough, but the idea would be that it almost becomes like a subscription, except the users are paying per each new release and maybe there is a little signal when users buy a new release because they want access to new features that the devs are working on.