The usual response here (from any vendor, not just an independent game developer) is to say you only support the latest LTS version of Ubuntu/SteamOS with the officially supported drivers there and that's it. You're absolutely right to do that. If you want obscure distros to be able to run your program, you can open source it and let them deal with the packaging/testing/maintenance. The fact that all the OS packages are open source is the only reason all the random distros are even able to exist, so you're already making it difficult for them when you don't do this. No reason to dance around that.