Hi. Is a Gen 5 magic keyboard compatible with a Gen 6 iPad Pro?

The currently available Magic Keyboard for iPad Pro 12.9" is compatible with the third generation iPad Pro 12.9" and later.

The fifth and sixth generation iPad Pro 12.9" are physically identical - as are the location of the Smart Connector and magnets that locate the iPad Pro with the compatible Magic Keyboard.

The third and fourth generation iPad Pro 12.9 models, lacking the miniLED XDR Display, were slightly thinner. As such, older versions of the Magic Keyboard, while usable, don't properly accommodate the thicker models.

You can compare the physical dimensions here - and within the associated specifications:

https://www.apple.com/ipad/compare/?modelList=ipad-pro-12-9-6th-gen,ipad-pro-12-9-5th-gen,ipad-pro-12-9-4th-gen

This is the compatible Magic Keyboard (in the U.S.).

Magic Keyboard for iPad Pro 12.9‑inch (6th generation) - US English - White