The only two ways to accomplish this:

val someExternalApi = SomeExternalApi()

fun flowExample(): Flow<Int> = flow {

    someExternalApi.addListener {
        scope.launch {
            emit(it)
        }
    }
}

flowExample().collect { println(it) }

are:

val _events = MutableSharedFlow<Int>()
val events = _events.asSharedFlow()

val someExternalApi = SomeExternalApi()

someExternalApi.addListener {
    scope.launch {
        _events.emit(it)
    }
}

events.collect { println(it) }

Or

val someExternalApi = SomeExternalApi()

fun flowExample(): Flow<Int> = callbackFlow {
    val callback: (int: Int) -> Unit = {
        offer(it)
    }

    someExternalApi.addListener(callback)
}

flowExample().collect { println(it) }

I would rather not use the callback flow since it's experimental and using the

sharedFlow

seems incorrect since it's intended purpose is

for broadcasting events that happen inside an application to subscribers that can come and go