I'm having a similar issue. I'm an old player that's just returning to the game.
But the mouse movement issue is only happening with Feral Heart for me, and no other games. I'm certain I'm tabbed into it correctly, but the cursor is stuck in the middle of the window, and I'm not able to interact with the window at all, using mouse or keyboard shortcuts.
I tried to follow the tutorial above, but I could not find an ogre.cfg file The only files I could find that had "ogre" in the name were .dll
I'm using windows 10 if that helps.