Inner beauty, to me, is a quality of life someone has that emanates so much kindness and happiness that others pay no attention to any outer nonbeauty.
I have known people in my life someone told me were not the prettiest thing in the world, but I actually had to look at them differently to see that. I had never noticed it before then. It never mattered even after noticing, and in a moment's time I forgot all about any shortcomings or possible ugliness. I am reminded of a teacher I once had that still, after decades, has that inner beauty most people cannot help but to notice.
I actually never remember trying to find it in myself, as I always noticed it in others.