6 Not Supported: Thunderbolt Displays
While the new iPad Pro models can be connected to a variety of USB-C external displays, the new devices do not support Thunderbolt 3 — the standard developed by Intel and Apple. That means you can’t connect the iPad Pro to Thunderbolt displays.
Mostly, that limits the number of external monitors and displays that your iPad Pro is compatible with. Most Apple-approved 5K displays, for example, run on Thunderbolt. Other standards, like HDMI, are supported.