Wired vs. Wireless
Basic problem is that NextDNS seems to work with wireless but not with wired connections.
I have two MacOS computers both work with wi-fi but neither work on wired networks.
One computer is a laptop that is on Catalina while the other is an iMac running BigSur.
Both computers are running PIA VPN turning off the VPN makes it work. I've tried to turning off the PIA DNS but that doesn't seem to help.
Update, NextDNS is now working on the BigSur iMac with both wired and wireless connections. After updates and reboots which seemed to fix something.
Still doesn't work with PIA VPN even if I tell PIA to no do the DNS.
Problem with wired connection on laptop is nothing to do with NextDNS. Computer is not able to maintain the wired link even with all VPNs turned off.