I'm also on Arch Linux. I don't have any problem launching Nier and getting to the main menu from steam. I do see the same failure when using steam-native. This is expected since Arch doesn't provide libgnutls26, which is what Proton 3.7-8 is linked against. Newer Protons link against libgnutls30, which Arch does provide. By using steam-native, you are preventing Proton 3.7-8 from finding the libgnutls26 that the Steam runtime provides.
Do you have a reason to prefer using steam-native?
Same problem on Solus 4.1
However, Denuvo appears to authenticate the license if run from bundled steam. After that, one can close the game, exit steam and restore the use of steam-native via Linux Steam Integration toggle.
Probably the issue stems from this: https://github.com/ValveSoftware/Proton/issues/1757#issuecomment-431571624
Hello, please retest this game with Proton 6.3-6 and see if any regressions have crept in since this issue was last evaluated.
proton 6.3-6x1 2021-09proton 3.7-8x1 2019-03
Compatibility Report
System Information
I confirm:
Symptoms
The game displays a dialog box (will put a screenshot here as soon as possible) stating that the servers could not be contacted. The available options are to retry and open a web browser.
This occurs when the proton version whitelisted by valve (3.7-8) is selected. Forcing 3.16-6 allows the game to be played flawlessly.
Reproduction
This can probably be reproduced on any system affected by the previous gnutls issues, that were subsequently fixed in Proton. This was reproduced on Arch Linux (native libraries).