Conceptually I want to do this:

// Expect file (commonMain)
expect class PlatformDir
    
// Platform-specific implementation for JVM
actual typealias PlatformDir = File
    
// Platform-specific implementation for Linux/macOS
actual typealias PlatformDir = CPointer<DIR>

The simple JVM type is accepted but the parameterized type of Linux/macOS is not:
Expected class 'PlatformDir' has no actual declaration in module for Native The following declaration is incompatible because number of type parameters is different: public actual typealias PlatformDir = CPointer
Type arguments in the right-hand side of actual type alias should be its type parameters in the same order, e.g. 'actual typealias Foo<A, B> = Bar<A, B>'
Actual typealias 'PlatformDir' has no corresponding expected declaration The following declaration is incompatible because number of type parameters is different: public final expect class PlatformDir
Moving the parameterized type first into its own typealias also doesn't work:

private typealias CPointer_DIR = CPointer<DIR>
actual typealias PlatformDir = CPointer_DIR

It still complains about the wrong number of type parameters and has this additional error:
Right-hand side of actual type alias should be a class, not another type alias
I'm very much a noob in Kotlin and JVM as well as Kotlin Multiplatform so I feel this must be possible without wrapping both in a class. Googling I can't find anybody discussing this and the AI chatbots seem to just clutch at straws that get more and complex and don't build either.