I have no idea how the made it into the stable build. It hardcodes 8.8.8.8 and 1.1.1.1 as the DNS servers, which breaks any local DNS resolution. There are a few solutions listed here.
If you’re running Hass.IO on Ubuntu, do the following:
vi /usr/share/hassio/dns/corefile
Change the DNS entries in there. Then do:
docker restart hassio_dns
And then restart HA from the UI. It should come back but will likely be overwritten if the container updates without this being corrected. Thanks to the instructions above for the pointer.