In an interview, OnePlus CEO Pete Lau told me (through a translator) that getting a phone on Verizon’s network wasn’t possible for OnePlus until Verizon launched its certification program for open-market devices or phones not sold by Verizon. Once that was available, it took OnePlus about a year to get its devices certified for use on Verizon. OnePlus also extended its network compatibility worldwide: the 6T now works on 233 carriers in 74 countries.
The OnePlus 6T has support for Verizon’s primary LTE band as well as features like VoLTE and Wi-Fi calling on the network. According to OnePlus, the Verizon experience should be like any other carrier: pop a Verizon SIM card in, and it should just work. If you don’t already have Verizon service and want to activate a OnePlus 6T on the network, you just have to go to a Verizon store, and it can be done.