I wanted to provide a link to something I found fairly useful, without the need to download large software programs or have watermarks on your pictures. This is just a web-page script so you don't really need an internet connection. Maybe you'd like to check out the HTML. Maybe everyone already knows about this page lol.
So, sometimes you might want to create a custom work of art on a flat, less distorted workspace where a Cubemap would be easier to visualize. Anyway. this will convert different map types to other styles of map types; like Cubemap (Horizontal Skybox) to Equirectangular or the reverse.
Just pick the map type and pick your map file (again nothing is uploaded, but I did have some trouble to really large files). Try it out!
Example: From this
WITHOUT the Panov2 watermark