Just fired up Voyager on Android to discover a notification-style marker above the settings/gear icon. Opening Settings doesn't provide any clue as to why. Taking it further by tapping each of the top level menu items also doesn't show why.
Okay, Voyager. Keep your secrets...
Edit: F-Droid showed that Voyager had recently updated, so I tapped the recent apps button and swiped up to close Voyager. When I reopened it, the marker was gone.
I'd wondered if that might be it, thanks.
I know the developer is active here, so thought it night be a good opportunity for them to address it ahead of more questions. ๐
I did an update all from the play store and it went away. Interestingly, Voyager was not one of the apps listed.