With the popularity of iPads and iPhones, it's natural that people ask if they can use a drawing table with their Apple Device.
The summary is:
You can use a pen tablet (screenless tablet) with an iPad or iPhone only under very specific conditions - with specific apps and specific tablets.
There is currently no way to use a pen display (screen tablet) with an iPad or iPhone.
Ibis Paint (https://ibispaint.com/) supports connecting a drawing tablet to an iOS device
ONLY via Bluetooth. Wired connection is NOT supported.
ONLY specific tablets models.
Read more about Ibis Paint and pen tablet at these links:
HiPaint supports connecting a drawing tablet to an iOS device
ONLY via Bluetooth. Wired connection is NOT supported.
It is unclear which tablets are supported or not supported. I tested it with a Huion Inspiroy Frego M (L610)
There are instructions in the HiPaint user manual explaining how to connect to a tablet.
https://www.aige-hipaint.com/support/manual/en-us
Wacom specifically calls out that their Intuos models do not work with iPhones or iPads in this document: Wacom - Does the Wacom Intuos pen tablet work with an iPhone or iPad?
Currently I don't know of any way to use a pen display with an iPad.
For example, if you connect a Wacom Cintiq Pro 22 to an M4 iPad here is what happens:
The iPad will treat the pen display just like a normal monitor
Using the pen on the pen display does nothing
Even though this pen display supports touch, if you put your fingers on it nothing happens.