How to show earths full extend as in scene2d?

I’m unable to show earths full extend as map. With a landscape viewport the I’m ot able to fully zoom out and show the complete earth. It depends on the actual aspect ratio of the viewport. EPSG:3857 (Webmercator) projection seems even more restricted then EPSG:4326.

With a viewport in portrait orientation on the other hand I can zoom out independent (with only one world copy). But I don’t have control over the viewport of my users any way.

I gess I’m doning something wrong or missing something, as showing earth with its full extend sounds like a baseline task.