It turns out it's actually possible to fall back to WPA2 in case the
authentication fails with WPA3. This was suggested to me in the hostapd
mailing list: add another network block with only WPA2 and lower
priority, for each network with WPA3. For clients with missing/broken
WPA3, wpa_supplicant will:
1. try the network block with higher priority first
2. fail and temporarily disable the network block
3. try the fallback network block and connect
This takes a little more time (still <5s) because wpa_supplicant
retries a couple times before disabling the network block, but it allows
old client to gracefully fall back to WPA2 on mixed WPA2/WPA3 networks.
To avoid downgrade attacks, clients with proper WPA3 should disable
this; in the future we may want to disable this option by default.
2eed89bbe1