Honestly, I'm not absolutely sure about this last. I've looked into Monogame. It's a game programming framework, rather like XNA (that it is an open source version of, since MS stopped development of XNA -- for whatever reason), rather than a full game engine with a scene editor, etc.
Monogame is supposedly great for Iearning low level graphics programming, or building a beautiful 2D or 3D game, with maximum control -- that isn't too demanding. At least for Windows. To develop for mobile platforms it seems to be more difficult and troublesome to use successfully.
I'm really only mainly interested in developing for Windows PCs right now, so developing for mobile platforms is not a major issue, but it could be in the future. I am, however, very interested in 3D game development, and Monogame really isn't recommended for that -- though it is certainly capable of it.
Monogame's development future seems somewhat questionable as well. Not all it's users are exactly thrilled with it either, though many do also seem to adore it -- despite its many troublesome quirks. This begs the question of whether or not it is worthwhile for me to invest time learning it -- even if it would just be a simple projects stepping stone into using a more full featured engine like Xenko.
Could I also not learn to do fairly simple projects at first using Xenko (including 2D), and just have that much further of a head start working in the type of engine I would end up wanting to use in the end anyway? I'd be interested in your opinion on that, but it also sounds like maybe a question I should ask on a separate thread? Honestly, I'm not sure.