If you look on https://www.steamdeck.com/en/software you can see that the home screen looks different with a colored background and blurred “taskbar”.
And if you scroll down you can also find that the library has a very different feel.
This can also be seen in this videos https://www.youtube.com/watch?v=WfoLRmKwnSI B-Roll of the Limited Edition OLED.
It’s part of the new Steam Client Beta, you can use it right now, though I’d argue it still seems a bit unfinished, the new visuals clash with a number of things that haven’t been changed yet
It doesn’t seem like you need to be on SteamOS 3.5 Preview to use it, just the Beta, since it’s part of Steam
Thats cool and I can confirm that its apart of the Steam Beta and not SteamOS 3.5.x. I think the QAM and “Steam” menus could do with a slight redo to fit better with the new theme but otherwise I think the Home Menu, Library and Settings look great compared to before! Most colors seem to be a bit darker than before so thats nice for us who like dark themes.