https://youtu.be/Am4B5f3J9Lk
After watching that, as a professional iOS developer I can tell you that probably Apple just cut off the support for this Line 6 something-to-lightning cable, so it won't work ever, unfortunately. That's why Line 6 cannot do anything on the software side from 3 months or so - it's not so big change for a software development team to update the sound driver to this newest iOS 13's one, come on, really. Shame...
If it would be a software/driver/sound class problem it wouldn't work with that adapter either. It's a hardware issue.
