This is true for lightning iPads, but for the iPad Pro with USB-C, any USB hub will work fine for plugging into a USB-MIDI-to-CV module.
I’ve personally had some success plugging the iPad directly into the Expert Sleepers FH-2 (USB-C to USB-C). The FH-2 leaves a bit to be desired in the configuration interface (and Safari on iPad doesn’t currently support WebMIDI, so the browser-based editor doesn’t work there), but once it’s configured, it works really well.
Simpler USB-to-CV modules may be easier to configure, and should all function well. For sequencing app suggestions, check the Your iOS arsenal thread.
The iPad should also work fine with class-compliant audio interfaces like ES-8, if you want direct signal control, rather than midi.