> Wine/Proton helps make the Win32 and DirectX APIs a sort of de-facto cross-platform standar
There are perfectly fine _actual_ cross-platform standards like Vulcan and OpenGL. If your goal is cross-platform, making a Windows app that you hope will be converted well enough is a strange way to approach it.
And yet, the win32 is the only one that is confirmed to work.
Example: Game Neo Scavenger is available for linux with binaries for them. They dont work in any modern linux because (I believe) they were compiled for a 32bits version of linux.
Do you know how you can play the game on linux?
Yes, using the windows version with lutris, which is 32bits too.
That doesn't help, most Linux distributions do not maintain ABI (library-program linkage) compatibility between major releases, and in the case of rolling distros half the system has to be recompiled when things such as libcurl, openssl, libc etc change. If these change, it's possible that anything compiled agaisnt the system version of it will no longer work without being recompiled
Windows goes back and beyond for compatibility with existing compiled software and Wine inherits that, is partially why Windows versions under Wine often have a higher chance of running than the native versions (ARK is a great example)
Projects like Flatpak attempt to solve this by the use of runtimes.
Game studios get a lot more mileage out of testing their games on Linux+Wine than bothering to build a Linux native version that will stop working within two years.
Steam has incentivized this with their Steam Deck Verified program. The Steam Deck being so popular means a lot of studios want their games to be verified on Deck, and if they're verified on Deck then they work in the Linux desktop version of Steam out of the box.
There are perfectly fine _actual_ cross-platform standards like Vulcan and OpenGL. If your goal is cross-platform, making a Windows app that you hope will be converted well enough is a strange way to approach it.