I recently decided to make the switch to OpenWrt 21.02 (and then 21.02.1) for my Linksys WRT1200AC router. After having done so, I have recreated the network configuration from scratch because it couldn't be imported from the previous 19.07.7 install.
Since then I experience issues with all devices which connect to the 5GHz band of the WiFi AP (please note that 2.4G and 5G use two different SSIDs). The connection is established but after a while (some hours) the device cannot access Internet any more, even if the link is still marked active; same behavior noticed on Android and iOS devices.
I disabled WPA3 after having read some people reporting instability, but nothing changed.
Before the upgrade to 21.02, everything went fine with the 19.07.7 release.
Interesting fact: my iRobot Braava Jet m6 house cleaning robot can't connect to WiFi at all while using my 21.02 setup, whatever 2.4G or 5G is chosen.
Switching back to my 19.07.7 setup, everything works OK: the Braava robot can connect and the connection is stable for all the connected devices (2.4G & 5G).
I remember that I had some similar problems with versions of the 19.x branch prior to 19.07.7. Is there some recent fix in 19.x that hasn't been backported to 21.x?
I've also found some related topics on the forum but none of them really match what I'm experiencing:
Also, someone reports an issue with 21-rc1 that is new compared to 19.x on a WRT3200 router (https://www.bountysource.com/issues/99322104-anybody-having-issues-since-openwrt-v21-rc1-on-linksys-wrt-3200acm-wrt32x-with-wifi). Don't know if it's related...
Does anyone have a clue on what's going on?