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).

Is that nondualism more similar to a mind-only kind or more like a matter-only variety? In the former, I feel like meaning is ontologically fundamental in some sense while in the latter meaning doesn't exist, and is just a figment of illusory experience---meaning is just overlaid onto an otherwise meaningless fundamental reality.

That being said, even in a materialism-only view, one can say that meaning is still there in an information-theoretic sense. Reality has real objects and structure, and an organism is sensing that and representing it with patterns of neural activity. When said organism communicates with another organism, there is an ontologically real correspondence between their neural activity and the patterns in the communication with the actual real world they are sensing and communicating about. That is the meaning of their communication, it "means" the particular arrangement of material reality.

I am more of a mind-only type of nondualist though (at present).

Depends on what you mean by "nothing". Are you a materialist? Dualist? Other?

Maybe truth is chaotic and even seemingly inconsequential truths can have effects far away.

Handbook of Panpsychism or start with wikipedia and Stanford online Plato encyclopedia. I've been reading a lot about that and idealism lately. I am leaning towards the latter view now.