Disable wifi and NAT on the TMO-G4AR device and use my own router.

Compos Mentis wrote:

I saw Nate Tater's video for doing exactly that. However that involves using a "business" sim and paying per GB. Not an option. The TMHI sim with not work in a 5G modem router. It is designed to fail. Been there, done that. Put the sim back in the TMHI device and it works fine. 

Double NATing  fails to maintain DNS, even though I use my own DNS settings. I don't play games either. I just want to be able to use a web browser without WIFI. Most of my devices are on Ethernet (wired).  I've played with my router settings and it is a losing game. Where I work, ATT has provided a cellar backup to our firewall. I can fall back to any one of three sources for redundancy.

I've been to a T-Mobile company store. They only want to offer me another TMHI device which I already have. If you don't have a business license, nothing will happen. 

I've had no issues with Comcast's modem in the past using my router. I was hoping I could save some money with TMO. I am starting to wander whether or not, if it is worth the trouble.

Are you setting DNS on the WAN or DHCP? Setting DNS on WAN is recommended as it will allow internal names to still resolve.