Yeeesss it works....
The following rule must be add additionally:
sudo iptables -A CLOUDRON_RATELIMIT -p tcp -m tcp --dport 631 -j ACCEPT sudo iptables -A CLOUDRON_RATELIMIT -p udp -m udp --dport 631 -j ACCEPT
And my cups conf has follow lines (only an excerpt)
Listen *:631 Listen /run/cups/cups.sock SystemGroup lpadmin
After that I add my own user during the installation of Ubuntu to group lpadmin to administrate cups and now it works well.