I'd like to fix a sorting bug. What should I dive into?

Assuming I’d want to take a shot at fixing https://volumio.org/forum/albums-album-view-not-sorted-correctly-t8295.html myself and submitting a patch, what should I be looking at?

Volumio-UI or something lower down in the stack, like the MPD controller?

Yes, the mpd controller:
github.com/volumio/Volumio2/blo … d/index.js

Submitted a pull request for this: