Here's a quick word about possible portability of Underrail because I get asked this a lot.
The reason why Underrail is Windows only is because it's built using C# and .NET, and based on Microsoft's XNA technology.
Now, because Microsoft has since decided to discontinue their XNA development I will also be moving away from it in the development of future games.
One of the possible alternatives is Monogame
, which as I understand is a cross-platform implementation of XNA based on Mono (the cross-platform .NET implementation). So if I decide to try out this technology in some future development I will test it out by trying to port Underrail to it.
So it's possible that as some point we will see Underrail on Linux and Mac, but that certainly won't be anytime soon and neither can I make any concrete promises regarding that.