When you plug a USB-C hub into your new iPad Pro, you will see a new icon appear in the iOS status bar, up on the right by the battery, Wi-Fi, and LTE status icons. It’s a little blue lozenge with an icon of an old-style Camera Connection Kit in it, and it appears for just a short moment.
The new icon is handy to let you know that your hub has been recognized, but it doesn’t always work as expected.