So it appears my Sonos S2 app has updated to version 80.0. This has led to some troubles with getting the app to update the music index of my collection on the NAS. The support page states that "update your music library" is unavailable and that
This setting is not currently available in the Sonos app for iOS or Android, but it will return in a future update.
As a temporary workaround, please use the Sonos app for macOS or Windows to manage and update your music library.
That's all nice and dandy, but my OS is Ubuntu.
Now what?