The Magic Keyboard for the iPad Pro doesn't include an Esc key.
It is possible to map another key to use for Escape in iPad's Settings > General > Keyboards > Hardware Keyboard > Modifier Keys.
This means giving up one of the other keys. CapsLock seems to be a popular one. But what if you need all those keys for other things. Luckily there is a shortcut for the Esc key.
iPad OS Escape key shortcut: ⌘ + .
Pressing the Command and Period keys at the same time works as an escape key replacement across most apps on the iPad.