While still in HVM mode, I tried emulating what they did particularly with the "Make sure that the update proxy is disabled in the firewall settings" step to my best extent on Qubes 4.0 (In the services tab I unchecked yum-proxy-setup, qubes-yum-proxy, qubes-update-proxy, qubes-update-check and updates-proxy-setup). Sadly, this also seemed to have no affect. The host AppVM could network but the Docker container in bridge mode was unable to.
Note that while doing this I was behind sys-firewall.