EDIT:
Unity Slider do in fact work for Unity builds on Linux when using touchscreen.
However, for some reason I need to click buttons or anything UI related 3 inches down to the right for me to click or move the slider.
Attached is a picture.
Blue is where the Button is.
Red is where I need to click on the screen to activate the button.
This is the same for sliders.
Sorry for the terrible drawing, I’m not an artist.
It’s like this for all scenes!