Sorry, I could not reproduce the “ERR_TIMED_OUT”. The log files seems to be ok.
It tried it with Win 10 and XP now:
On WIn 10 Edge, Firefox and Chrome are working.
On Win XP only Firefox ESR works, the other browsers have problems with auth but I have to use old browser versions on XP because the newer ones are not supported anymore.
Proxy (manually set, FQDN): proxy.domain.local
Turn off any proxy script autodetection function.