Right this minute you could find very fast internet (fiber) in rural areas with very inexpensive housing. I have a relatives in the Dakotas & Nebraska with better internet than I have in Denver. Some of them live in town and some of them live in the country. A lot of it seems to depend on local government having the drive to get rural access funds from the FCC.
As another said, eastern Montana could be brutal if its not something you are used to. There are extremely hot and extremely cold days (in the -30s degrees F) possible. It will be really windy and really brown (its very dry) for much of the year. You might also be shocked by how much some people drink/use other substances and how they get around when incapacitated. (There is no Lyft/Uber). There will not be a lot of young singles around, either.
I personally don't think there will be a big boom because of Starlink for housing. At the end of the day, internet is just a small factor in what makes a place desirable to live. Climate, distance to city/airport, local bars & restaurants, scenic beauty, and local activities all factor a lot, too.