Notifications are not detected to be not working on Raspbian

Quoting @sebkur from #327 (comment 74864):

Notifications do not work and are not detected to be not working (which might be the thing that we could ideally detect). I think it's not much our fault though. After installing x11-utils, I have notify-send which also doesn't work. It fails silently, much like our app. I think there's just nothing installed on that system that shows the notifications that are being sent to libnotify.

The message is

libnotify-WARNING: Failed to connect to proxy

ldd --version shows:

Debian GLIBC 2.31-13...