In your screenshot where you see PROTON Experimental. Change that to PROTON version 6.3. Now try. If the game fails to load again, then go to the next version down. You just keep doing that until the game launches and plays right.
I am going to assume you have selected your proprietary Nvidia driver in additional drivers?
Make certain you are not using an Nvidia driver that has the word TESTED in it, because it causes nothing but problems for most that use it, including me.
Regarding sound, you have to choose the output that works for your setup, I have no idea what that is, since its not my computer or setup, only you know that. But, if you would like an easy way to change your output sound from the taskbar, here is a nifty tool.
Do you ever feel like your computer never listens to you? I do everyday and I swear its causing me to have a complex! With this nifty extension, I am able to select the audio output device, its quicker then going into Pulse Audio and doing it there.
Just an FYI, if the OS can't interface with the hardware because of a bad driver, then Steam also can't launch a 3D game. As that requires 3D acceleration. You are using the wrong driver IMO, as it has TESTED in the name, and its most certainly causing you issues.
460 PROPRIETARY should run fine on your older GPU without issues. It does however look like your list has not been updated in awhile. Have you installed any updates recently for your OS, including driver updates?
I ask, because I find it odd that 495 is not listed in there. Anyways, I put much effort into my last post, because I knew that I was going to be going to bed, and wanted to try and cover all basis at once.