Edit the /etc/NetworkManager/NetworkManager.conf file, and set the following entry in the [main] section:

dns=systemd-resolved

Reload the NetworkManager service:

# systemctl reload NetworkManager

Force adjusting of /etc/resolv.conf

  netconfig update -f

Verification steps

Verify that the nameserver entry in the /etc/resolv.conf file refers to 127.0.0.53:

# cat /etc/resolv.conf
nameserver 127.0.0.53

Verify that the systemd-resolved service listens on port 53 on the local IP address 127.0.0.53:

# netstat -tulpn | grep "127.0.0.53:53"
tcp   0   0 127.0.0.53:53   0.0.0.0:*   LISTEN   1050/systemd-resolv
udp   0   0 127.0.0.53:53   0.0.0.0:*            1050/systemd-resolv

https://www.reddit.com/r/WireGuard/comments/1foqw8w/wireguard_issues_relating_to_dns_after_upgrade_to/ https://www.procustodibus.com/blog/2022/03/wireguard-dns-config-for-systemd/

Remove DNS entry from wireguard conf. Not using WG dns though

Some domain cannot be resolved (e.g., google.com but bing.com works). After updating system, may be relink the resolve file:

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

Check which route the DNS query goes:

  ip route get 1.1.1.1
  
  dig google.com @1.1.1.1
  resolvectl query google.com

• https://unix.stackexchange.com/questions/328131/how-to-troubleshoot-dns-with-systemd-resolved

• https://geekflare.com/linux-server-local-dns-caching/