dnsextd messages in console
As the man page says "dnsextd is a daemon invoked at boot time, running alongside BIND 9, to implement two EDNS0 extensions to the standard DNS protocol."

My guess is that you are getting these errors because dnsextd is running on your Mac and trying to talk to BIND, but BIND is not running. You can check this by running the following command. If it comes back blank, then BIND is not running.

pgrep named


I think the solution to this problem is to just turn dnsextd off using the below command. Unless you are running this Mac as a DNS server for other devices then I'm not sure why you'd need either running.

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.dnsextd.plist