It sadly doesn't work on my PC on W10, using the latest FIrefox 64-bit build. Tried every fix out there for Firefox and Windows to be able to have my 5.1 speakers be used, but no dice!

Can confirm, does absolutely nothing on Win10 with newest Firefox. Window opens, but all bars are empty/cant be changed and the buttons change color when clicked but that's it.

"Uncaught (in promise) Error: Script 'moz-extension://72149dd7-64d2-4a9d-b1af-4f8eea9e6f73/audio_processor.js' result is non-structured-clonable data audio_processor.js
apply self-hosted:2610
applySafeWithoutClone resource://gre/modules/ExtensionCommon.sys.mjs:689
applySafeWithoutClone resource://gre/modules/ExtensionCommon.sys.mjs:688
wrapPromise resource://gre/modules/ExtensionCommon.sys.mjs:960"