My fix was to reset the device’s network settings (but I fear it may not work for all hardware versions).
After upgrading and reconnecting to WiFi after the mandatory reboot, all my Apple devices insisted on using the WEP protocol – whose security has been broken for some time.
Lots of things I tried didn’t work…
- Turning WiFi off and on again – off-&-on-again isn’t always the answer; who knew?
- Airplane mode;
- Forgetting the network; &
- Hard reboots – of both devices and router.
Eventually, I twigged that under Settings -> General -> Reset, there’s a Reset Network Settings option. You are prompted for confirmation and your PIN. The device will reboot and, once restarted, you’ll need to select your WiFi SSID re-enter your password.
A small price to pay for privacy!