I came here to ask the same question.
As reported above, the mopidy.conf file is a very bare bones affair after following the automated setup instructions, and even adding the [local] and media_dir settings (and restarting) does not pick up the settings.
I used a fresh Buster Lite image on a Pi Zero with Pirate Audio. Tried it a few days ago, had the above problem. Tried again yesterday with a freshly downloaded Buster Lite image, same problem.
[Following these instructions](https://learn.pimoroni.com/tutorial/sandyj/getting-started-with-pirate-audio) [Whilst also referring to these](https://github.com/pimoroni/pirate-audio/tree/master/mopidy) to do an automated setup as I'm a noob to mopidy.
Possibly of interest, the automated install had some errors near the end :
Mopidy configuration has changed, see summary below and make sure to update /etc/mopidy/mopidy.conf!
Your previous configuration was backed up to /etc/mopidy/mopidy.conf.backup-2020-03-06-17-16-57
diff: /etc/mopidy/mopidy.conf.backup-2020-03-06-17-16-57: No such file or directory
Also, following the auto install and a reboot as per instructions, /etc/mopidy does not exist! Only after a 2nd reboot does this appear, but in the bare bones format noted above - there’s no [local] part in it.
And attempting to run sudo mopidyctl local scan gives this output :
Running “/usr/bin/mopidy --config /usr/share/mopidy/conf.d:/etc/mopidy/mopidy.conf local scan” as user mopidy
usage: mopidy [-h] [–version] [-q] [-v] [–config FILES] [-o OPTIONS]
unrecognized command: local
Hope this info is useful and a fix can be looked into