In Rust, you'd generally use functions that return iterators or Tokio's streams for Linq-style tasks. Check out the "Complex Queries" example on http://diesel.rs for an example of what a Linq-like library looks like in Rust.
Linq, ick. It's a performance nightmare. No one knows what it is actually doing in the background so firstly, everyone writes horrible O-cubed performance with it, and then it is a series of random poking around to try fixing it.
Depends if you're using it with ORMs or not. It's equally as useful with data in memory. Definitely slower for some things though (yes, it's always slower in one sense... But its also easier to make parallel, so it can even out in the end)
Still, I now prefer doing such things in Rust.
Yes, it does. Also a C# programmer. I really like Rust. About as easy to use to transform, filter, group etc, but considerably faster.