Multiple Consoles (PS4's) on Same Network

We've noticed a similar issue in Black Ops III, but no, I haven't found a working solution in the PlayStation forums either (incidentally, I have another thread going there with no responses...).

https://community.us.playstation.com/t5/PlayStation-Network-Support/MULTIPLE-PLAYSTATION-4-s-ONE-NETWORK-NEEDS-FIXED-ASAP-Confirmed/td-p/44774137 - suggests that there are certain port openings one should watch for in their UPnP configuration.  With those openings, one should basically reset the UPnP server on their router and then manually forward the ports to the PS4's.  I tried that and the PS4's still opened ports through UPnP that weren't the ones I was forwarding.

https://community.us.playstation.com/t5/Consoles-Peripherals/Two-PS4-s-on-the-the-same-network-cause-NAT-incompatibility-with/td-p/45132971 - suggests that static IP's should work, or failing that, put one PS4 in the router's DMZ.  Neither approach has worked for me.

https://community.us.playstation.com/t5/Consoles-Peripherals/2-PS4-s-on-the-same-network-not-working-getting-error-NW-31295-0/td-p/45181843 - suggests that using ethernet on both consoles (rather than wifi) should fix the issue, but I've given that a shot too, no dice.

In other news - the second PS4 in the apartment broke down this weekend.  Appears to be the PSU.  Going to manually replace it this weekend, but until then the only real problem now is sharing the one remaining PS4 lol