Seems like valve read this post :D
https://steamcommunity.com/games/1675200/announcements/detail/4674264042200389436

I think it’s related to the monitor I was plugging on HDMI. With a different screen it works better.
But I still have sometimes the displayport screen not turn on after sleep, and the deck crashing when unplug/replugging it :(

I wasn’t clear in my post, but I have a monitor plugged via HDMI too, and that’s the one having trouble either turning on, or being stuck in 480p. I will try with a different monitor or cable.

With only the displayport monitor it works well

It’s false if I remember correctly. Steam prohibits you from selling steam keys outside the store for less than the price on steam. They don’t forbid you from selling cheaper elsewhere