I found the answer here
I add these rules on the host
iptables -I ufw-user-input 1 -i br0 -j ACCEPT
iptables -I ufw-user-output 1 -i br0 -j ACCEPT
iptables -I ufw-user-forward 1 -i br0 -j ACCEPT
Thanks for the help, to configure properly the bridge without lxc-net.