Some Issues Running miniDNServer on Ubuntu
miniDNServer listens for DNS query messages from clients on the standard UDP port 53. However, on Ubuntu, systemd‑resolved occupies port 53 by default. To resolve this port‑conflict issue, simply stop and disable the systemd‑resolved service:
sudo systemctl disable systemd-resolved
If /etc/resolv.conf on your Ubuntu system is a symbolic link pointing to /run/systemd/resolve/stub-resolv.conf, it is recommended to remove this symlink:
sudo unlink /etc/resolv.conf
After that, create a regular file and configure the nameserver parameter as needed.
The systemd‑resolved service is not enabled by default on Debian systems (great!), so this problem does not occur there.