I've been using OpenWRT on my Linksys WRT1200AC since July. I installed 19.07.7 and loved it and had zero problems. I came home from school last weekend and saw that the current firmware was 21.02.1, so I did a sysupgrade to that firmware and wiped my configuration as was recommended.
21.02.1 works just fine for every device I own besides any Apple device like my iPhone XR, all of which are running iOS 15.1 currently, where connectivity is pretty bad. I can connect to the network fine, but every ten or twenty minutes the connection to the Internet will drop out of nowhere with the iOS settings turning the network icon orange and displaying "No Internet Connection." Sometimes it will come back on its own, but I usually have to toggle Wi-Fi off and back on again to restore functionality. Internet connectivity is completely halted when this occurs until I reconnect to the router. This problem never occurred in the six months I was on 19.07.7.
This happens on both the 5GHz and 2.4GHz bands. My 21.02.1 configuration is exactly the same as my 19.07.7 config save for the things that may have changed behind the scenes between versions, and it's all stock except for running WPA2-PSK-WPA3 mixed on the 5GHz band and WPA2-PSK on the 2.4GHz to accomodate an old printer I own that can't understand WPA3. This is the only thing that changed between my config for 19.07.7 and 21.02.1 along with enabling KRACK countermeasures -- I have tested using the exact same settings as when I ran 19.07.7, and the issue with iOS devices still occurs.
This does not happen on any device connected to the network besides iOS devices. I have a laptop with a network card built in 2009 that works more consistently than iOS devices on 21.02.1.
How can I fix this?
Thanks so much for any help!