Hey guys I am also using a Focusrite with a SM-5S and also had such bad input lag the game was unplayable. I switched to a USB lapel mic I had lying around and the game instantly became playable, I think unfortunately the Focusrite just adds too much input latency for a game like this sadly! One way to help resolve it would be for the dev to add a latency adjustment slider so you can push the samples of your recording back in time by a fixed quantity if you know you have input latency. Rhythm games often have an input latency adjustment tutorial for things like this.