Just go to their home URL and click the Local feed. (In your example, just go to https://sh.itjust.works/) You won't be logged in there, but you can still see the feed. If you want to actually post, you'll need to go to that post on your local instance, though.
Edit: Completely glazed over the 'voyager' part of your question. You might be better served asking on the app community; I'm afraid I don't have an app-specific answer for you.