linux-embedded-hal VS jailhouse

Makes sense. The EtherCAT master component can be loaded as a kernel module (for Etherlab), which I think is somewhat independent of the user code. The rust code interfaces with the driver through syscalls. There is some discussion about Rust with PREEMPT_RT here https://github.com/rust-embedded/linux-embedded-hal/issues/45 but it looks like it is still open.

You could run it inside something like jailhouse hypervisor (https://github.com/siemens/jailhouse) if you want to give it direct dedicated "baremetal" access to hardware. You could do this inside of a buildroot linux image. This would need a customized simulator.

Yes indeed, and Siemens even has their own hypervisor: https://github.com/siemens/jailhouse

Yeah, I think that is what something like https://www.toradex.com/computer-on-modules/apalis-arm-family/nxp-imx-8 is useful for, where it has a separate core. Or even on linux you can use isolcpus to get pseudo-isolation. There are also hardware hypervisors like Jailhouse (https://github.com/siemens/jailhouse) which can completely isolate hardware resources and I suppose might prevent the GPU from causing an issue with realtime task. But this definitely affects ease-of-use and probably requires a reduced feature set in the language (no dynamic allocations) and lots of unsafe code.