The experience I described was with the 14 but I also tried in the 15 pro something similar and had same experience.
For now my approach is to use a external microphone with a longer cable and a notebook, and this works, but it would be nice to make this work with the iPhone.
I daily an (newest model) SE and got some wireless lavalier mics that plug into the lighting port. They work well and were cheap. Have to carry them around. Not name brand or anything. Though I hope to get some from rode.
I don't use the phone productively, everything I tried I endup concluding it can't do? So it's only use is complaining about things in hacker news for killing time.
The most recent idea was trying to use it for sounds but I had the mentioned issue. Does the lavalier works for environment sounds or you only use for voice?
Mostly use it for recording technical talks at Python Atlanta meetups (I’m an organizer). Ambient sounds are not a priority. But I’ve used it to capture the sounds of a fresh water beach (which sounds much different than salt water). I did have to remove the cover on the phone to be able to do a proper a/b sound test. Maybe your cover isnt helping?