I am using DNS over https and have firefox 63 setup as follows
-Operating DNS system set up with a fake non responsive DNS value
-The URL for DOH- https://mozilla.cloudflare-dns.com/dns-query
When I set Firefox to use network.trr.mode to a value of 3 which I understand to mean use only the DOH DNS values and do not fall back to any other, firefox fails to to resolve any sites. This worked prior to Dec-7-2018 but not anymore. Can you offer an explanation?