Behaviour of Android 9 Private DNS with restricted networks and a quick comparsion of DNS over TLS providers (or why I use Quad9)

I got Android 9 (Go Edition) three days ago and as right now I am still unable to find results on how its Private DNS (DNS over TLS) behaves when port 853 is blocked I typed my own post.

Test: automatic mode without DoT capable server from DHCP ; the setting says “automatic”.

Test: DoT with port 853 blocked ; Android reports that the WLAN network has no internet connectivity…

Test: automatic mode with DoT capable server from DHCP ; Android says that DoT is “enabled”

Test: DoT + Captive Portal ; I get the captive portal prompt asking me to login to the network as usual…

For more details and the reason why I use Quad9 you have to read the post or forum threads where I have discussed my DNS choices.