I've had the same problem with my AirPods Pro and Big Sur. Running Big Sur v. 11.0.1 and the latest update for the AirPods. As @Repidepi mentioned, I was also not able to delete any of the files within the /Audio/Plug-Ins/HAL folder - I wholeheartedly agree with this comment.
However, @Natashaag31's comment about changing the sounds within the Audio MIDI settings worked for me! I hope this helps with anyone who had the same struggles as me.
saurish
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