I originally had Ubuntu 18.04 and was trying to get the sound to work with all these and couldn't get it all to work. It was a nightmare. All in the list above worked individually but fixing one to work would cause another not to work. Then I saw Ubuntu Studio and thought that would be better. So far, it is not.

You will want to run the jack audio server. Use qjackctl to setup and run/manage jack. You won't be able to use firefox with jack unless you compile it from source. You can download the audio/video from the browser and play it with something like audacious.

I also recommend using a proper sound interface. Internal (built-in) audio interfaces are often really bad. I like the maudio fast track series because its good enough and affordable.

Let us know if that gets you any further.

Jason