I had previously been using a setup where I had a POD Go as my audio-in device and then ran a line out of the headphone jack.
It was working great, but recently it stopped working. Basically, now anytime I plug my cable into the output jack of the iPad, MIDI Guitar stops recognizing the POD Go.
This has nothing to do with MG2/3; it’s an iOS limitation. And it is a peculiar description because iOS/iPadOS’s coreaudio system does not allow you to have separate input and output audio devices, and as far as I know, it has never allowed such a thing. Your POD Go should handle both in and out in the iPad audio realm when using MG2/3 in standalone.
The only exception to this might be if you use a host application that has the ability to parallel route audio to your iPad’s headphone jack. Some hosts can do this. IIRC, Audiobus 3 and AUM both can.