Short Version: Destiny 2 does not send a UPNP discover or the packets required to open up ports to the firewall. Extended Version: UPnP is enable on my router (Ubiquiti ER-X). UPnP, as it is configured, is working. Destiny 2 on PS4 will open the ports required for gameplay, and other PC titles (such as Warframe) are also opening their required ports. I used Wireshark and performed a packet capture during the startup, character select, and tower load phases, and not once did I see an SSDP request, or the appropriate packets sent for opening the required ports. While my wife and I can usually play together without too much issue, adding additional people to the mix can sometimes result in disconnects for random people in the fireteam.