The following assumes that you have a USG that is already online and connected to Pentanet with IPv4.
To configure IPv6 on your Unifi USG, first open up the Networks menu, first select your WAN network, and then set the IPv6 connection type to ‘DHCPv6’ with the prefix delegation size
Now, back in your Networks menu, select your LAN network. Under IPv6 Network Configuration, select the ‘Prefix Delegation’ option and enter the prefix size
56, enabling IPv6 Router Advertisement as indicated.