Brave Engineers - maybe make this an option as it is soooo annoying?
SHIFT + COMMAND + ”.” or use a Terminal command to Reveal Hidden Folders.
Go to Macintosh HD > Library > BraveSoftware > Brave-Browser > Default > Extensions > “gokgophibdidjjpildcdbfpmcahilaaf” > 22.214.171.124 > Music > “Success.mp3”
Now, that might vary a little for you, depending on your system and version, but you’ll figure it out. It is somewhere in that Extensions folder.
Now, take that ridiculous .mp3 file and replace it with a blank text file by the same name, including the extension. You may need to change the extension once more after saving it. I didn’t try deleting the file in case that would create a failure, but that may work too.