View images on CompactFlash on iPadPro using Lightning to USB 3 adapter?
Apple says:


  Add even greater capability and versatility to your iPad Pro by powering the Lightning to USB 3 Camera Adapter with a USB Power Adapter. Then you can connect USB peripherals like hubs, Ethernet adapters, audio/MIDI interfaces, and card readers for CompactFlash, SD, microSD, and more.


It sounds like using a USB card reader is supported. However, you may need to plug a USB-C power adapter in to your Lightning->USB3 adapter to get it to work. Thankfully there are USB-C battery packs if you want to stay mobile.