I'll definitely stick to Arch Linux / SteamOS and I'm so glad they ship it like that and that they helped make Proton so great over the years.
Bringing Steam to Linux and porting all own games was the first big step for Linux gaming as a whole.
Starting off with Proton was the second.
The Steam Deck is the third and it will be a massive one.
Many
tutorials will spawn out of nowhere telling any newb how to setup RetroArch, Dolphin, office apps, Lutris and god knows what else under Linux and it'll be the first time a really big (and growing) user base will get in contact with Linux and use it as the main OS for gaming. Great times ahead and I'm glad to always have played around with Linux ever since so I will get the most out of my Steam Deck when it arrives*.
*after Q2 2022... (crying in silence)