2 things to note:

When offline, switch into steam offline mode to launch games, gets round some of the hanging on launch issues

Try connecting to WiFi from the steam decks desktop mode? Probably a router issue though.

I bought Reus 2 (A puzzle god game) at launch last month - game changer!

Finally a game that I enjoy playing on the deck and actually want to play after work on my commute etc. highly recommend it.