Hey Mark @oneofmany , you and I might be the only ones using this Asus with USBridge So I’ll try to help
Does your router broadcast a 5GHz network with a different name to the 2.4GHz network? Or just a single SSID?
Like I have two different WiFi networks: One called Sean2.4G and one called Sean5G and I manually choose which one I connect to, with each device in the house. Actually now I only have a 5G WiFi network (I’ve now manually disabled the 2.4G radio of the router) but that’s what I used to do, so you get the gist.
If you have two different names also, you should be able to see the 5GHz one in DietPi’s WiFi settings page and just select the 5GHz network and enter it’s password.
Your router shouldn’t force 5GHz connected devices onto the 2.4GHz network, unless you only have a single SSID that covers both?