A 2014 Silverado i recently drove is probably very similar. You have to press the”Media” button repeatedly to cycle through to USB audio. If you press it once, it goes to Bluetooth regardless if you have a Bluetooth device connected.

if your truck has an auxiliary power converter plug (like a regular 110V outlet) plug a standard Iphone micro-brick into it and connect the phone via USB to that. it will not interfere with the radio and it seems to charge a LOT faster than the built-in USB ports on the truck.

The port on those trucks(And just about every GM vehicle for that matter) are set up for a radio that CAN use audio from the USB port. the fact that your radio doesn't do it is academic, the phone is still seeing it as an audio available connection and switching to the Lightning output for audio.

Get a cigarette lighter USB adapter.

Driving the truck tomorrow so will update for any that care or have a similar issue.

Secondary issue for many of the on board USB ports on vehicles is that they are almost all low power...a quality accessory charger will charge faster.

I obtained a third party charger and that works. Have audio from phone while plugged in. Still think someone screwed up the design somewhere. There is no audio from USB on this truck. Thanks all.