This broke the seal for me, so I finally decided to figure out why Steam wasn't working for me but worked for some people...
When I first installed Linux, I somehow installed 2 versions of Steam - the deb and the flatpak version.
Apparently flatpaks have less privilege and this is causing issues. So I purged both! I did it in an incredibly awful way as I bounced through tutorials, initially doing
[dpkg --list] ... Yes I manually purged anything that said Steam, I think this was mayhaps not the best option as when I installed steam with [sudo apt install steam], it didn't even boot anymore. Yikes!
So naturally I searched for my problem and found this steam thread: https://steamcommunity.com/app/221410/discussions/0/3094509155628372846/
I'm sure there was some redundancy, but I followed 1, 3, 5, 6, then input [steam] into the terminal. It worked! I noticed it removed more libs than I had managed with my initial purging, probably related XD
EVEN BETTER, THE GAME BOOTED! I don't know if that's because previously I had run the UE4PrereqSetup_x64.exe and finished the installation, which got rid of my C++ runtime error, but that's what learnin' on the jobs all about.
I noticed exit didn't work, so there will likely be some issues. Someone mentioned on reddit that their TV didn't work?
I hope this helps my Linux homies out there. I'm using Pop OS LTS with some duct-tape to make Nvidia work. Best of luck!
Edit: I forgot to mention, I also run it with Compatibility: Proton Experimental