Sadly, I did manage to reproduce issue on older 6.10.6... It seems it's a race condition of sorts (maybe it's just "faster" reproduced in 6.11.5), as on one computer I rebooted 20 times with WiFi starting up successfully, but on other PC (some OptiPlex) it reproduced after 12 reboots on 6.10.6 too...
I though I could workaround by some system timer, by detecting "wifi" device with "unavailable" state, and restart NetworkManager. This does seem to help if "unavailable" state happens when re-pluging dongle while system works, but not after failed boot, where it just enters "disconnected" state for whatever reason, even if "autoconnect" is set to the connection. This is very bad. This means we can't use Debian + WiFI in "untended" machine that MUST have WiFi working after any random reboot it might experience.
