Experience with 4G LTE sim card routers

[shep]

I'm in a rural area with marginal ADSL service. It looks like some new technology could be a cost effective upgrade for me and I was wonder if anyone else is utilizing this?

The Details:

The Device:
https://ltefix.com/shop/routers/lte-...26-lte-router/

Cat3 modem for US Cell providers
https://ltefix.com/shop/modems/sierr...-4g-lte-modem/

Howto put it together:
https://ltehacks.com/viewtopic.php?f=21&t=233

There is also a youtube video that illustrates assembly and states it essentially a MoFi with $200 savings.

Comes with older OpenWRT software that can be easily upgraded:
https://openwrt.org/toh/views/toh_ex...Brand*~%5D=ZBT

T-mobile has an unlimited data plan for Seniors, I qualify .

I do not know sqat about cell phones or sim cards. My main concern is making sure it works with an ATT, or T-Mobil or Verizon sim card in my area. Anyone getting access via a Cell phone, tablet sim card?