Enable Masquerade to allow port forwarding
sudo firewall-cmd --permanent --add-masquerade
Forward TFTP UDP port 69 to 6969
sudo firewall-cmd --permanent --add-port=69/udp
sudo firewall-cmd --permanent --add-port=6969/udp
sudo firewall-cmd --permanent --add-forward-port=port=69:proto=udp:toport=6969
sudo systemctl reload firewalld