The NEWS link details a bit more:

https://github.com/ruby/ruby/blob/v4_0_0_preview2/NEWS.md

What is interesting to me is the `Ractor.shareable_proc` changes that solved a bug for a use case I was having. And in general fixes for Ractors make them more appealing to use right now, even though they have not removed the `Experimental` flag from them. They are still missing a built-in concurrency primitive like channels or a lock free queue; I'm curious what they will settle on, Ractor::Port is nice but not enough.