Update and (relatedly good) news!
You can use dspMixFx under iOS 11 under the right conditions.
First - connect the Interface to your device, second - start dspMixFx, third - power on the Interface. The Interface is detected, dspMixFx can be used to change the settings. If you disconnect the device by dropping the cable and reconnect ist, the device will no longer be detected.
You must power off the device again, then power on and it will be detected again. Odd behavior but better than nothing.