If Picard is installed via Snap all "Open folder" actions do not work. This is for example the case for "Open containing folder" for loaded files, but also for opening the plugin folder or config folder in options.

This is supposed to work via xdg-desktop-portal automatically, and it does work for the Flatpak install. But there seems to be an issue with this on Snap, see https://forum.snapcraft.io/t/xdg-open-or-gvfs-open-qdesktopservices-openurl-file-somelocation-file-txt-wont-open-the-file/16824/14 and https://bugreports.qt.io/browse/QTBUG-83939

As a workaround xdg-open could be used