Not seeing printers on iPhone 12 pro max with vpn

I have successfully set up my iPhone XS and iPad Pro 12.9” gen 3 to see my printers via VPN by using Printopia and a printer profile I install on my phones.

The printer profile basically tells the phone the local IP address of the printers when connected remotely, the resource path and ports to use. I need that profile installed because you can’t receive mDNS over VPN to hear the Bonjour advertisements.

It works like a charm on both, but I’m trying to get it to work on an iPhone 12 Pro Max, and while the VPN profile works correctly, the Printer profile is either ignored or it simple can’t see the printers anyway. It can ping them, however, and can connect to shared folders on the remote network, etc.

The only differences I know of is that the 12 pro max is iOS 15.1.1, while the other phone and iPad are 15.1.

Also, the Pro Max is on T-Mobile via Consumer Cellular MVNO, while the other phones are on AT&T.

Has anyone ran into a similar problem? It’s just weird that identical settings and profiles do not work the same on only the iPhone 12 pro max.

The VPN is l2tp run on an older Mac Mini running MacOS 10.13.6 and Server 5.6.3 (the older one, before Apple removed all the good stuff).