According to a tweet from reporter Steven Aquino, mouse/pointer support works on both iOS 13 and iPadOS via USB and Bluetooth. However, “this feature is not really designed for old school cursor support like some think” he adds.
“Apple likes the idea accessibility features are getting mainstream looks (cf. mousing on iPad) but they strongly emphasized this was designed and developed expressly for a certain segment of user,” Aquino writes. “In other words, curb your enthusiasm. ‘This is not your old desktop cursor as the primary input method’ is what I was told [by Apple].
Developers using the first beta of iPadOS have found that you can control the software using a mouse plugged into your iPad. The feature was not announced by Apple, and it is a part of the accessibility options rather than a default.