So essentially, you were offered a remedy that allowed you to continue playing the game, you rejected the remedy, and now you're complaining? They're obligated to support the old version of the client forever, regardless of any obstacles to that?
If you bought it to play on a 32-bit Mac would they be obligated to port it to 64-bit? Would they be obligated to port an OpenGL-based client to Metal after Apple's deprecation?
Lets get back to reality here. Epic bought Rocket League. They said they wouldn't change anything during the purchase. 6 months later there is no more linux client.
You're telling me that because I can emulate the game it still exists. If I accept this premise than literally all games are linux games and the concept of platform goes out the window. It's absurd.
Proton is a compatibility layer (just like WINE), not an emulator, unless you're planning to play on ARM64. It's just like using VKD3D or MoltenGL instead of using a native graphics API, plenty of games do that.
They're letting you play the game you paid for. I can understand being unhappy about the loss of a Linux client, but by all reports the Proton version runs better, so what's the actual problem other than your ideology? Epic is a corporation, not a religion.
