SteamDeck Wi-Fi problems

Hi,

I am a new Steam deck user. Device is SteamDeck OLED 1TB. During the setup phase you have to enter Wi-Fi details. As much as I tried to enter the password the connection always hanged and then failed. My Wi-Fi router had WAP2/WPA3 Personal set 5GHz&2.4GHz.

I read that there seem to be problems with that WPA setting so I changed to the router to WPA2 AES. No change. I had to resort to my LAN USB-C adapter to setup the deck for the first time and update the SD software.

Now in my carage I have a simpler router which is 2.4GHz and WPA2 TKIP. This one connected without problems.

I am wondering what kind of magicry is needed to get it to work with my main home router. All other devices worked right off the bat, even my old AV -receiver.

I did try tinkering with the desktop but there If I try entering the Wi-Fi password now it wants to setup some kind of password vault and not sure If that helps.

If anyone is interested the main router is Sagemcom modem from DNA (operator), DNA Mesh Wifi F-3896

EDIT: I also tried an OPEN (no password) guest network with my main modem and that hanged and failed too.