How do I make a map's background transparent in a layout?

Question

I am trying to add an overview map to my layout. The main map is projected while the overview map is a 'globe' (image below). I want to make the white part of the overview map transparent.

I have made the background transparent in page properties and I have turned off background for both maps. There is no option to make the background of the main QGIS window transparent.

Is there anything else I can do other than export separately and add it as an image with transparency values?

EDIT: Forgot to mention, I have looked at How to export a map with a transparent background in QGIS? but it didn't work.

Answer 1

Nevermind, I'm just an idiot.

I forgot that I had an inverted polygon turned on to add some fading to the outer edge. The solid fill of this was filling the rest of the layout.

Thanks anyways.