Hi, I'm ~~Troy McClure~~ Localhorst86.
You may remember me from legendary ~~films~~ posts like "Mommy, what's wrong with that man's face?", "Lead paint: delicous, but deadly" and "My Steam Deck decides to spontaneously disconnect from my dd-wrt router".
About 2 weeks ago, I made a post about strange connectivity issues with my steam Deck on my 5GHz WiFi. I'm glad to announce that I was able to further pinpoint my specific issue and how I was finally able to establish a stable 5GHz WiFi connection on my steam deck.
I figured, an update post could be helpful to give it more visibility.
I was getting fed up with my connection issues, so I decided to get a new, dedicated WiFi6 accesspoint, to see if it aleviates the issue. The access point arrived about 10 days ago, and once set up, my steam deck was able to hold a continuous connection the the 5GHz WiFI on it. Downloads would start at full blast of my ISP (~30MB/s) for about a minute, then slow down to about half that speed (12-14MB/s), but it was faster than my 2.4GHz WiFi and it wouldn't disconnect at all.
I tested and observed this for about a week, and it remained stable. With the AP being a fairly cheap device, it wouldn't support dd-wrt or openwrt, so I had to live with the limited options of the factory firmware of the device, that includes a limited combination of network modes (11a/n/ac/ax or 11a/n only), so I left it at (a/n/ac/ax).
But on my DD-WRT router (the one I had issues with), the network mode was set to 11ac only, because that gave me the best reliability and speed for my Oculus Quest 2 airlink setup.
I've then decided to set the network mode to "mixed" (11a/n/ac) and see if it would fix the issues. Unfortunately, this alone did not. I've then played around further with the network settings, and reduced the channel width from 80MHz to 40MHz, and that - in combination with mixed network mode - would result in a stable connection that downloads at full ISP blast for the first minute, then slow down to about half the speed, like it did with the new AP.
[TL;DR] If you have issues with the steam deck maintaining a 5GHz WiFi connection, make sure you enable mixed network mode for the Access Point, and reduce channel width to 40MHz.
I assume you already tried disabling WiFi power saving in the steam deck developer settings, right? Just asking because you mentioned this in neither of your two posts and because I also fixed my 5GHz connectivity issues this way.
EDIT: Nvm, overlooked it in your first post.