How to charge and use headphones with an iPhone 7 or later at the same time
At times I need to connect my iPhone to my car stereo's AUX IN port (when my car's bluetooth is flakey and I do not have time to reset it) However, the podcast app I like, Downcast, will only keep the iPhone awake if the phone is charging. The iPhone 7 and later (7 Plus, 8, 8 Plus, X), do not have a headphone jack, so how do I charge and use a 3.5mm audio jack (headphone) adapter at the same time?

The answer is an adapter that can do both. When I was looking, it was early on and I choose this Steanum model. This adapter has worked for me and there are many more choices available now that have similar capabilities.
Search 3.5mm Audio + Charging Adapters on Amazon
I talk about why I like using Downcast here.
Search 3.5mm Audio + Charging Adapters on Amazon
I talk about why I like using Downcast here.

Downcast on the App Store
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Added 2018-03-26 <> ID 18032602
Versions - Downcast 2.9.32
Added 2018-03-26 <> ID 18032602
Versions - Downcast 2.9.32