No sound from Ardour or Hydrogen using JACK on new install of Ubuntu Studio 20 on 2013 Macbook Pro

The initial settings for JACK on first install of Ubuntu Studio 20 on a 2013 Macbook don't work for the laptop's built-in audio. A few changes need to be made to the defaults.

1. Start QjackCtl from the upper-left system menu, under Audio Production -> Audio Utilities.
2. Hit the "Setup" button on the middle-right.
3. You may want to use a different Preset Name so you don't lose any settings you currently have.
4. Set the Interface to hw:PCH,0 (i.e. the CS4208 Analog option).
5. Click the "Advanced" tab.
6. To the right of the Channels I/O label, there are two dropdowns. Set both of these to 2.
7. Click OK, then either Stop/Start QjackCtl or restart it completely.
8. Make sure QjackCtl is in the "Started" state.
9. Start Ardour. Under the Window -> Audio / MIDI Setup menu, make sure the Audio System indicates it's using JACK.
10. In Hydrogen, under Options -> Preferences, under the "Audio System" tab, make sure it is either automatically or explicitly using JACK.

You can verify that it works in Ardour by clicking the Metronome button, which is the second from the left (beneath the Session menu), then hitting the play button. You should hear some sounds.

Other audio programs (e.g. Audacity) might also need to have their preferences set to use JACK while QjackCtl is running.