Yeah, it's absolutely a catch-22. That said, most Linux distros come with closed source repos deactivated out of the box. The nicer ones will at least ask you during the install process, but some don't bother. It's less about convincing the devs to port and more about exposing the stuff that already exists.

And Proton shows that a translation layer that works reliably on Linux isn't impossible, it just needs the right amount of focus and investment. I don't know how far the current tools are from that, though. Which is interesting, because I do use Linux on the daily and I haven't even bothered to check in ages, instead moving to Windows for that, which tells you something.