If I was hiring for this sort of position, I'd want them to talk about the difference between hard and soft real time. I'd want to know whether or not they were familiar with embedded software development standards and what sort of things are restricted from "normal" environments when you are working in the embedded environment.

The last thing I would want to see is lines of code on a whiteboard. I'd want to see how they'd structure their code, not whether or not they remember C/C++/Rust/language-de-jour syntax.

All of the proposals for questions that I've seen in this thread are for basic programming skills. Not whether or not the person knows the environment we are hiring for.