did a search uitoolk background gradients.. obviously expecting -linear-gradient should of known its still not supported still, how many years are required to get the absolute bread and butter of css into uitoolkit already. I hate all these work around hacks its not just the hacks its that you can’t use the visual designer code the css directly and see the updates without compiling and going into play mode 
Ironically getting a gradient on a button in ugui was there from the start I believe.
share the same pain, but toolkit team mentioned that its coming in Unity 6.7, so really hpong it atleast alpha launches end of july/august
It can’t come soon enough, hopefully it’s supported with stacking multiple backgrounds like css3