This problem seems to occur when you are either live streaming yourself or viewing a live stream. It also appears to be independent of your hardware (which you observed when you switched to your earbuds and continued to have issues.) The problem appears to be purely Discord's.
Some configuration that eliminated the problem for me was heading into Settings, opening up Voice & Audio, scrolling down to the Advanced section, and making sure that...
- Noise Suppression is off.
- In the Voice Processing section, Noise Reduction is off.
After disabling these two settings, my audio appeared to come through as clear as though I wasn't watching a live stream. I also started a livestream myself and had others join, and I sounded perfectly fine to other users.