I would guarantee it’s not a software update. I have a Express 3900EU with the same issues in July, ~18months old. Mine will only connect if its within 1m of an access point. It’s not the AP, I’ve tried 3 different Ubiquiti models on 3 different firmware versions, tethering to various iPhones, 2 different travel access points. All legal frequencies / channels. WPA on and off. When using the ‘secret’ wifi screen I NEVER have any signal on Antenna2. With an AP ~10cm away it shows Strength:32, Ant1:49, Ant2:0.
I posted the issue months ago and have had no response from ROKU. I therefore take this as planned obsolescence
What is more annoying to me is that I do not want a wireless device. I would far rather have one with a built in ethernet port or the ability to use an OTG network adaptor ie.
https://www.amazon.co.uk/UGREEN-Ethernet-Adaptor-Chromecast-Network/dp/B01N1X28F1
Don't mention the Ultra, its not available in the UK and does not support some UK channels - BBC iPlayer...