Tracked down the #NetBSD 11 WiFi problems I was having on i386! IT WAS EERO'S FAULT.
Eero has some wonky behaviour when it runs in WPA3/WPA2 mixed mode, sometimes it seems to return NULL packets during auth.
NetBSD11 has wpa_supplicant upgraded to 2.11, which blocks this kind of behaviour.
The fix turned out to be really simple: force wpa_supplicant to only use WPA2 and also specify "ieee80211w=0" in the network config.
I've got a working install; AND #Lagrange also built perfectly this time. I am really quite happy.
I will be even happier when I finally replace these stupid AP's, I have grown to detest them.