Can I use USB-C to headphones on iPhone?
The USB-C to 3.5 mm Headphone Jack Adapter lets you connect 3.5 mm headphones and other audio devices to a USB-C port. Plug your USB-C to 3.5 mm Headphone Jack Adapter into the USB-C port on your device and plug the other end into your headphones.
Is there an adapter for Lightning headphones?
This adapter lets you connect devices that use a 3.5 mm audio plug to your Lightning devices.
Is there a DAC in the Lightning to 3.5 adapter?
The Lightning to 3.5mm headphone jack adapter includes a DAC with CS4272 Chip, and Apple’s chip number 338S100104. You can google CS4272, it has 24-bit 192kHz 114dB output capability, though I wonder if Apple still limits it to 24-bit 48kHz.