First of all, I want to thank @ludouzi for making fooyin. For years I've looked for a serviceable music player on Linux, never quite finding something as comparable to foobar2000. The first day I tried fooyin, I was blown away by the polish, customizability, and huge breadth of features.

Problem

Anyway, I store all of my music on a Raspberry Pi running OMV attached to my router (so I can access my music on every device in my house).

In /etc/fstab I simply run this on startup, mapping the directory to ~/pidrive:

//<LOCAL_IP_ADDRESS_OF_RASPBERRY_PI>/pidrive /home/kevin/pidrive cifs user=kevin,pass=hunter2,x-systemd.automount 0 0

If you use Flatpak, fooyin will be sandboxed and map drives using the literal /run/** directory mapping. This is OK for non-NAS folders.

The issue is that between reboots, the /run/** path for /home/kevin/pidrive will change, and fooyin will fail to find your library:

Solution

This AskUbuntu answer was helpful: https://askubuntu.com/a/1094903

In short, make sure that you give fooyin access to the directory where your music is.

sudo flatpak override org.fooyin.fooyin --filesystem="/home/kevin/pidrive/public/Music"

Then you can mount your network directory normally!