This seems to work, Ubuntu is hoarding port 53 though even though local services are shut off.

Config/DNS/undo.sh

@@ -0,0 +1,44 @@
+# 2023-07-29
+# Config/DNS/undo.sh
+# Easy way to stop using this container.
+
+function start-service {
+	service=""
+	if [[ -n $1 ]]; then
+		service=$1
+	else
+		echo "ERROR: A parameter was not provided for start-service, aborting."
+		exit 1
+	fi
+	if [[ -n $2 ]]; then
+		echo "ERROR: A second parameter to start-service is not expected, aborting."
+		exit 1
+	fi
+	systemctl enable --now $service &&
+		echo "$service started successfully!" ||
+		echo "$service was not found, no problem."
+}
+
+echo -e "\n*** Stop the docker container ***"
+docker compose down
+
+echo -en "\n*** Restore the DNS file "
+if [[ -e /etc/resolv.conf.save ]]; then
+	echo "from backup ***"
+	cp /etc/resolv.conf.save /etc/resolv.conf
+else
+	echo "with Cloudflare ***"
+	echo "nameserver 1.1.1.1" > /etc/resolv.conf
+	echo "nameserver 1.0.0.1" >> /etc/resolv.conf
+	echo "options rotate" >> /etc/resolv.conf
+fi
+echo "/etc/resolv.conf:"
+cat /etc/resolv.conf
+
+echo -e "\n*** Turn on any local DNS programs ***"
+start-service systemd-resolved
+start-service dnsmasq
+
+# Finish
+echo " "
+exit 0