Q: what printers are compatible with ipad pro?

if it support apples generic general printing interface called airprint it will work out of the box

otherwise you need to rely on a printing app made by the printer maker in app store and if the maker does not have an such then find one of the other print from a wide range of different printers app (they usually cost money)

This support article lists the printers that support AirPrint. -AJ