I purchased the MAX BR1 Pro 5G and have a Tmobile and a Verizon Card. I was trying to set it up so if one slow or fails the other would pick up. Also, I wanted to configure to pick up the best signal. However, I only see 1 cellular connetction and I have to manually select which one to lock onto and then it reboots, etc
Or you can force the issue, by specifically identifying only one SIM card to be employed (and then test, manually, which one is best for your needs at that point in time).
Get a 2nd BR1 Pro 5G. Setup the 2nd device on the ethernet WAN port of the main device.
The flipping back and forth becomes tedious real quick as you move from place to place and then constantly trying to figure out which carrier is best in a given spot. Even still that carrier can become bogged down while your there and yet all the signal strength is solid. Signal strength is not a guarantee of performance. I also do not like paying for service on 2 carriers and only using 1 of them 90%+ of the time. I work remotely and use SpeedFusion for reliability above and beyond just having basic failover of sessions between 2 carriers.
I have 2x BR1 Pro 5G in my campervan with roof mounted Panorama mimo antennas.