Cannot update user profile data – getting error

I went it to Users > All Users and tried to update my bio (I’m the admin), but when I try to save the changes I keep getting this error – “Error:?Sorry, that username is not allowed.”

I’m not editing the user name (I couldn’t even if it wanted to, since the admin username is not editable). Is this a known error? I’m not able to update any user information (including my author bio) due to this error.

I’m on WordPress 6.4.2 and not using any special user/author plugins — this is just the normal WordPress User interface.