Explanation of issue: when I plug in headphones (any pair of headphones), the line out icon appears instead of the headphone icon (see image below).
As a result, no sound comes through the headphones, although there is definitely mild feedback that does come through.
Phone: LG G4
Things I've tried:
Different pairs of headphones
Turned phone off and on again (with headphones plugged in and without)
Checked all audio related settings
Downloaded SoundAbout, but even this doesn't help, as it's not an issue of the phone misunderstanding the type of headphones, it thinks they're something else entirely. I did get some audio coming through the headphones after selecting "Wired Headphones" and telling the phone to ignore the headphones being plugged in, but it was very quiet and distorted by feedback.