[Discourse/Community] Translation missing: en.discourse_push_notification

Issue:
Push notifications from the Community forum (Discourse) include a message indicating an English translation is missing.
“Translation missing: en.discourse_push_notification…”

Details to reproduce:

  1. Turn on some kind of notification level for new topics in a category.
  2. Wait for a new topic in category.

OS: Android Pie
Device: Google Pixel 2 XL

Screenshots:

notes:
I have some familiarity with the community software (Discourse). Usually this issue is due to a missing translation or minor bug.
Usually this issue is fixed by updating the Discourse software to latest - as the issue has likely already been fixed.

Alternatively adding the translation manually via settings or reporting the issue over at https://meta.discouse.org and later updating after the issue has been fixed.

I think this is the hosted Discourse version - so Discourse themselves would need to patch.

@cookywook is the one with all the answers though!