FYI - There's a serious bug with Mode 3 on the BT home hub router.
Like a lot of people, I have to operate my hub with mode 3 enabled so that smart plugs, light bulbs etc can connect.
The trouble is every time BT updates the hub, mode 3 seems to get screwed and 2.4 GHZ devices can no longer connect. In addition WiFi seems generally unstable with regular lost internet connections on 5GHZ even though the hub is connected to the internet. Had this happen several times now, it seems to reset some sort of configuration related to Mode 3.
The solution - After an update has happened:
1) Reconfigure your hub to Mode 1 and reboot.
2) Reconfigure your hub to Mode 3 and reboot.
And then suddenly all your 2.4 GHZ devices can connect again. It's a pain in the backside, but at least there is a solution.
Paul...