Glad to read this is working. Sorry to read it was difficult to get to this functioning sound state.
I had my fingers crossed for your nVidia proprietary driver install. There was a time (~5 years ago) when it was reasonably common for a nVidia proprietary driver to break sound (back then it turned out to be a permissions issue that had a work around to add regular user to group ‘audio’ ) but that issue has been solved for sometime. Hence I was hoping that your sound would work with the proprietary driver, indicating that that old problem has not resurfaced.
Thanks for keeping us appraised of your progress.