interact VS bastion

There's also interact which feels more like a beam remote shell. Caveats is that you need to setup the endpoints ahead of time, and that it just gives you a basic expression parser, not a full language like Erlang/Elixir do.

How is this better / different than https://github.com/bastion-rs/bastion ?

There are attempts to implement an Erlang/BEAM-inspired reactor/runtime/executor/ecosystem for Rust's Async, in particular Bastion. (There are also Lumen, Lunatic and Async-Backplane/Async-Supervisor.)

I would be interested in an example showing how to build a robust runtime like bastion with fault tolerance.

But the issue you're referring to, building a fault-tolerant web server where you can have granular control over killing background jobs regardless if they're blocked on a syscall, totally requires using this kind of software architecture. See Bastion.

Bastion, a Rust async runtime inspired by the beam distribution and supervision model

I don't really know much about erlang, but I think this may be along the lines of what you are thinking of: https://github.com/bastion-rs/bastion

(I also don't really think the linux kernel people would be interested...)

This reminds me of bastion. Looks like it attempts to fulfill the same needs, though I guess Lunatic has native WASM support whereas bastion might require some tweaking to have it work? Haven't worked with bastion, so that part of harder time with WASM is just a wild speculation. On the other hand bastion looks much more mature. Probably /u/vertexclique could give a more informed opinion about the difference between the two ;) I really like what these projects are putting forward.