It might be that you have change one of the audio settings in developer settings. The Disable Audio Routing setting.

I noticed that it usually happens when the phone is on the charger. Normally when I take the phone out of the charger is when I experience the bug.

I'm experiencing the same thing on my S21 FE. The storage just goes to 0b/0b and I have to restart it everytime. This started recently after updating to OneUI5

I have tried but whenever I plug them in I get a notification saying "the connected USB device isn't supported".Also I prefer wired earphones. When getting the S21 FE I assumed any type c earphones would work.

I have tried but whenever I plug them in I get a notification saying "the connected USB device isn't supported".