In brief: T-Mobile is best known for its relatively fair (by modern standards) cell service and data plans, but the company has been making an effort to expand its reach into the home internet world as well. As of today, T-Mobile has been relatively successful in this regard: it has expanded its fairly-priced LTE-based internet service to more than 130 additional cities.
That's a significant service expansion, and it certainly lends credence to T-Mobile's claims that it will be bringing Home Internet to half of all US households within the next half-a-decade or so.
The newly-supported cities are far too numerous to list here, but T-Mobile has done the hard work for us over in its announcement post. The cities are dotted across Michigan, Minnesota, New York, North Dakota, Ohio, Pennsylvania, South Dakota, West Virginia, and Wisconsin. Overall, T-Mobile appears to have chosen a nice mix of rural and urban-leaning states here.
T-Mobile's Home Internet service, for the unaware, comes in at $50/month, without any data caps or router rental fees. The caveat is that you'll be expected to install the necessary wireless equipment yourself, but that process isn't too difficult for the mildly tech-savvy.
On the upside, all taxes and fees are including in your monthly payments, and you won't be locked into any yearly contracts. In terms of speeds, most customers will get around 25Mbps, which isn't great, but it's still better than what many US citizens have access to at the moment. Additionally, those speeds will get a sizable bump when T-Mobile rolls out 5G to its Home Internet customers, though that will likely come with a price increase.
You can check if T-Mobile's Home Internet service is available at your address using the company's coverage-checking tool.