I'm solo developing a spaceflight simulator on Linux (using the Godot engine), exporting binaries in both Linux and Windows. It turns out that I really didn't need to bother with the Linux export anyway because Steam runs the Windows version on Linux without any problems. The ONLY thing I'm still having trouble with under Linux is Steam VR on the HTC Vive. It works. Barely.
Interesting, do you think game devs in future will just target windows/proton and not bother with native Linux ports?
Though in my case, I currently offer demo/beta releases for both Windows and Linux directly from Github. If I ultimately elect to release my game under a GPL license, then supporting both Linux and Windows directly would make sense.