What is the common census on the topic expect/actual vs using interfaces? In my KMP project I do use expect actual, but only where I have to (basically it is a workaround for my props interface, which need to be

external

on my JS project and that doesn't fly for the other platforms, so there I expect/actual the interface). All the rest is simply an interface with implementations on different platforms and my dependency injection wiring it up. Are there guidelines for this?

They both have their pluses and minuses, depending on your needs. expect/actual can do things that interfaces can’t, like constructors and top-level properties and functions. But you can only have a single implementation with expect/actual, so if you want to be able to swap out a test double then interfaces are better. I tend to expect/actual configuration-level stuff and some utilities, and use interfaces otherwise.