UniFi USG multiple public IPs config (sauce: https://blog.wefixit.at/unifi-security-gateway-add-an-additional-public-ip-with-nat/)

config.gateway.json

{
  "interfaces": {
    "ethernet": {
      "eth0": {
        "address": [
          "10.0.0.1/29",
          "10.0.0.2/29"
        ],
        "firewall": {
          "in": {
            "name": "WAN_IN"
          },
          "local": {
            "name": "WAN_LOCAL"
          },
          "out": {
            "name": "WAN_OUT"
          }
        }
      }
    }
  },
  "service": {
    "nat": {
      "rule": {
        "3000": {
          "description": "DNAT 10.0.0.2 TCP/8080 to 192.168.0.2",
          "destination": {
            "address": "10.0.0.2",
            "port": "80"
          },
          "inbound-interface": "eth0",
          "inside-address": {
            "address": "192.168.0.2",
            "port": "8080"
          },
          "log": "enable",
          "protocol": "tcp",
          "type": "destination"
        },
        "5000": {
          "description": "SNAT 192.168.0.2 TCP/8080 to 10.0.0.2",
          "log": "enable",
          "outbound-interface": "eth0",
          "outside-address": {
            "address": "10.0.0.2",
            "port": "80"
          },
          "protocol": "tcp",
          "source": {
            "address": "192.168.0.2",
            "port": "8080"
          },
          "type": "source"
        }
      }
    }
  },
  "firewall": {
    "name": {
      "WAN_IN": {
        "default-action": "drop",
        "rule": {
          "1000": {
            "action": "accept",
            "description": "NAT 10.0.0.2 TCP/8080 to 192.168.0.2",
            "destination": {
              "address": "192.168.0.2",
              "port": "8080"
            },
            "log": "enable",
            "protocol": "tcp"
          },
        }
      }
    }
  }
}