I think that makes a lot of sense, it would be nice if they clarified if you could BYO router. My guess is you can, as long as it has a sim slot, but can't be too sure. Make sure T-Mobile coverage is good in your area first as well

https://www.pcsforpeople.org/ is another organization with low-cost internet for low income households. they some have hardware, too. they've expanded a lot since their first location opened in minnesota in 1998. (note: i am not affiliated with them, i just occasionally refer people to them)

That looks pretty good