iPhone 15 Pro supports USB sound cards which means 3.5mm Binaural Microphones is an option!

Tested an old Andrea Electronics USB Soundcard and a Roland CS-10EM with the iPhone 15 Pro. It works great! (Except one probably should put phone into airplane mode to minimize antenna interference).

Binaural enthusiasts.. this is the solution you've been waiting for!

I'm going to assume any standard USB-C Soundcard should work.  

I ordered a generic USB-C Soundcard to test and it turned out it is MONO only.

An audio interface card is better, but if you get a sound card, make sure it accepts stereo 3.5mm input.