I'm not well-read, so know nothing about Sarte. I'll have to look it up to understand that idea!

I think perceptions/experiences are literally all there "is," just a massive complex web of interacting perceptions. What we experience is simply how the experience of others appears from the outside. It's kind of like Bernardo Kastrup's analytical idealism, except I think that I think the instantiation of the individual mind precedes the bodily form (i.e. kind of like Eastern ideas on a soul reincarnating).