Apple's ultra high-tech iPhones of 2017 are giving T-Mobile the cold shoulder. The network's early deployment of its 600 MHz LTE network will see no official support from other manufacturers until at least Q4 2017.
https://www.notebookcheck.net/T-Mobile-s-new-8-billion-LTE-expansion-will-not-support-iPhone-8-or-iPhone-X.249176.0.html