OnePlus 3T supports LineageOS
OnePlus 3T supports LineageOS and 6 more android device supports LineageOS. Do you want to buy OnePlus 3T then good news for you can use LinegateOS, which is customized operating system for Android?
There are many android custom operating system available in the market but for your new device OnePlus 3 you can try Linegate OS supports Android Nougat 7.1 and Nougat 7.0
New Lineage OS support many android phones like LG G3, HTC One M7 (Verizon), ZTE Axon 7, HTC One M7 (GSM), Samsung Galaxy Tab S2 9.7 (2016) and Samsung Galaxy Tab S2 8.0 (2016).