I'm agree with you on "Apple just cut off the support for this Line 6 something-to-lightning cable" but I have faith that will be fixed eventually. I think they reduced the power given to an external device connected to the iDevide on iOS 13, sure this can be fixed through a software update (from apple), if you connect the Sonic Port to the iDevice using the lightning cable you can see the hardware details, apple could make an exception to this device (related to the power needs).
Line 6 official response is here:
Let's wait the next iOS 13 update and hope apple has addressed this. I have seen that this isn't the first time the Sonic Port has suffered from this. You can see on this forum, post from several year ago, similar to this related to a major iOS update, and then got fixed, I thing we are in the same situation.
Sonic Port (and VX) is a good product (I like it) but this is an inconvenience that hope be the last...