I've been using a WASD V3 mechanical keyboard with my iPad Pro 12.9 (Gen 2), iPad mini 5, and iPhone 8 Plus – and they've all worked perfectly until I updated to iOS 13 beta 2 (on all three devices).
With iOS/iPadOS 13 beta 1, no problem on all three. But after installing beta 2 to all three, only the iPad mini 5 and iPhone 8 Plus work with the keyboard – the iPad Pro 12.9 (Gen 2) does not.
I connect the mechanical to these devices with the same Apple Lightning to USB3 Camera Adapter – just switching the adapter from one to another, as needed – and have the Lightning port on the adapter connected to an Apple 30W power source.
I have two of the Apple Lightning to USB3 Camera Adapters and have tried both with the same results – the mechanical keyboard will not work with the 12.9, but works on the iPad mini and the iPhone.
I'm now using the Apple Wireless Keyboard with the 12.9 Pro, but would like to return to the mechanical keyboard. There's every chance that the next iOS 13 beta release will fix this, but if I could fix it now, that would be nice.
I do find it odd that it works on the iPad mini 5 running the same beta 2 software, so I'm thinking that it has something to do with the iPad Pro 12.9 (Gen 2) itself, rather than the iPadOS 13 beta 2 software.
Any thoughts would be appreciated. Thanks.