oneplus 6T MTP option not available in USB debugging mode.
How to set MTP file transfer mode as default on Android 6.0 Marshmallow (root req'd) - PhoneArena
Connecting in MTP mode
Help] Problem connecting OP3 to computer in MTP mode
No USB MTP/PTP menu? Just dial *#0808# to enable USB Storage Connection Mass Storage Mode — Android 4.4.4 (Samsung Tmobile Galaxy Note 4), Ubuntu 14.04, Windows 8 | orange narwhals
How to connect a USB MTP device on Linux - PCsuggest
My OnePlus 6T does not show MTP mode after connecting USB
6.0 marshmallow - How do I change the USB mode with a keyboard? - Android Enthusiasts Stack Exchange
Android USB Connections Explained: MTP, PTP, and USB Mass Storage
4.4 kitkat - How do I disable this MTP connection popup upon USB cable connection? - Android Enthusiasts Stack Exchange
Android USB Connections Explained: MTP, PTP, and USB Mass Storage
Solved] Fix: Android File Transfer Could Not Connect to Device
Connecting in MTP mode
How to Enable MTP Mode on Android? - YouTube
Android Device not Connecting to PC over USB in MTP Mode