Note to myself: if you play with sound-themes on your #Librem5 (and probably any other #MobileLinux device) and you seem to be stuck with the default sound theme (freedesktop) then delete ~/.cache/event-sound-cache.tdb* and restart #feedbackd.
@me Note that this should not be necessary if all things work correctly. From what you wrote there it looks like a bug in the Librem5 sound theme package.