Wireless Joint

Carrier: AT&T Distance_to_Tower: 0 to .5 Mile Type_of_Device: ASUS RT-AC68U Type_of_Modem: Sierra Wireless EM7455 Firmware: 9999999_9904609_SWI9X30C_02.24.05.06_00_GENERIC_002.026_000 Antenna_Setup: 2x 3dBi Omnis Cable_Type: 6cm RP-SMA Pigtail Optional_URL: https://www.speedtest.net/result ...

30MHz 2CA B2+B12:
!GSTATUS:
Current Time: 22016 Temperature: 40
Reset Counter: 1 Mode: ONLINE
System mode: LTE PS state: Attached
LTE band: B2 LTE bw: 20 MHz
LTE Rx chan: 800 LTE Tx chan: 18800
LTE CA state: ACTIVE LTE Scell band:B12
LTE Scell bw:10 MHz LTE Scell chan:5110
EMM state ...

I've written a bash script to automate the entire process of setting up any of the EM/MC74XX series modems (Generic, Dell, Lenovo). This assumes you have the Sierra card inserted into a USB enclosure.

From the script description:
- Only for use on Ubuntu 18.04 LTS LiveUSB
- All Needed Packages ...

Is there a reason for going with 2x WG3526-P instead of using 1x WG3526-P and a USB enclosure for the second modem? ROOter has modem load balancing built in.

As for power requirements:
802.11af does 15.4 watts
802.11at does 30 watts
12v 2.5A is 30 watts.

That all said, I doubt there is any ...

5MHz B26, ouch. That is gonna be an issue. Total peak bandwidth on a 5MHz carrier in 2x2 MIMO is ~37Mbps.
See: https://frankrayal.com/2011/06/27/lte-peak-capacity/

Your SINR and RSRQ are also very low. So the fact that you are getting terrible speeds is not at all surprising. You have about the ...

Well, for starters, that is not a Sprint tower you are connected to. You can tell because Sprint does not have any Band 4 towers.
If you enter AT!GSTATUS? a few times, you should see it cycle through a few carriers over the course of a few minutes. The modem will do this with no SIM or with a SIM ...