First things first, yes, I have followed the troubleshooting guidelines. My earbuds work with other devices and the volume controls on the right side still work on my Note 20 Ultra.
The right ear bud of my AKG USB-C headphones is silent after the most recent update, and I believe the issue is that the Note 20 Ultra is outputting all media in mono.
Case in point: YouTube, Facebook, Netflix, etc? All silent on the right, volume on the left.
However, when adapting audio under Settings>Sound and Vibration>Sound Quality and Effects>Adapt Sound...the right earbud is crystal clear!
...until it gives you an example of your new, "personalized" audio, only in mono.
This headphone glitch is a known issue that is largely being ignored. Please look into this further than throwing basic troubleshooting guidelines up again.