However, the replacement

onReceiveOrNull

is already imported, but, not being used.

I had the same issue. It’s not obvious from the first sight, but the extension function is only declared for

<E : Any> ReceiveChannel<E>

- only for channels that have non-nullable element type. If you have a channel with a nullable element type then the extension function won’t be picked up and instead a deprecated member function is still used.