Edi464, If you know there are T-Mobile towers close by which could provide solid, clean signals to your home that would be the best place to start. You might look at cellmapper.net and locate T-Mobile 4G LTE and 5G NR towers around your location. T-Mobile will offer 30 days to try out the router but it is hard to know the status of the T-Mobile solution where you are. Talking to T-Mobile about that might help get a little more clarity. Other users in your area might be able to provide some insight but it could be hit or miss. Avoid jumping out of the frying pan and into the fire. Take a little time to do some research.
I have not seen any special offers for getting home internet customers by paying for the competitor’s router. I would guess Verizon wants to charge for their router due to the contract. Who knows if T-Mobile will offer such a program. Their program offers change all the time it seems. I have not seen any indication they are doing such a promotion.