I have a 26c working with an iPad Pro 2018. Presonus says this USB-C series is designed for Mac, not IOS, so they don't officially support it (IOS) and will close support tickets related to IOS.
That said, it works for me after trying a few things.
- I can connect the 26c directly to the iPad Pro using USB-C to USB-C. The iPad will power the 26c, however you're now out of ports for charging or connecting a MIDI device.
- to resolve this I did two things: I purchased an multi-port adapter for the iPad, which has USB-C for power, HDMI, and one USB port. Then I connected a powered USB Hub to the USB port on the multi-port adapter and I connect my 26c and MIDI keyboard to the hub. II'm also powering the iPad from the the multi-port adapter.
This all seems to work with no issues. I can power and use the 26c, the midi keyboard, and the iPad simultaneously. And I still have a port available for HDMI/Monitor.