Stonehearth uses Chromium already for the UI only, which is cross-platform already. Getting the UI to work cross-platform basically just means using the right Chromium binary. However, the rest of the game is written in C++ and Lua. Getting that to work cross-platform is more of a chore. Electron unfortunately wouldn’t help things much but it’s a nice suggestion!
The renderer is written in OpenGL according to the FAQ so that’s another big hurdle skipped for the eventual port process. The game logic should also largely perform as expected under Linux, since Lua much like Webkit can simply use the appropriate version with the same behaviour. Theoretically it should run now, if it compiles at all; unfortunately, we can’t really know that for sure.