Where can I find a simple circle to draw it around a point feature. I can change symbol fill color as well as symbol border color. But I didn't find a way to set fill color to no color.
Set the alpha channel of the fill color to 0.
in the symbol properties, you can change the symbol type from "Fill" to "Border: simple line". This way you do not have a fill. (I am sorry if these are not the exact name, but I am translating from a non English version. However I'm sure that you can find it)
you can just make the opacity of the stroke color zero
