[Update] Set iptables-legacy as alternative on Debian systems

update.sh

@@ -485,6 +485,11 @@ while read NAT_ID; do
   iptables -t nat -D POSTROUTING $NAT_ID
 done < <(iptables -L -vn -t nat --line-numbers | grep $IPV4_NETWORK | grep -E 'MASQUERADE.*all' | grep -v ${MAILCOW_BRIDGE} | cut -d' ' -f1)
 
+echo -e "\e[32mChecking for iptables-legacy...\e[0m"
+if update-alternatives --list iptables 2> /dev/null | grep -q /usr/sbin/iptables-legacy; then
+  update-alternatives --set iptables /usr/sbin/iptables-legacy
+fi
+
 DIFF_DIRECTORY=update_diffs
 DIFF_FILE=${DIFF_DIRECTORY}/diff_before_update_$(date +"%Y-%m-%d-%H-%M-%S")
 mv diff_before_update* ${DIFF_DIRECTORY}/ 2> /dev/null