For many use cases where the best tool so far was Channel, Flow has become the new best tool.
As a specific example, callbackFlow is now the best approach to receiving data from a 3rd-party API’s callback. This works especially well in a GUI setting. It couples the callback, a channel, and the associated receiving coroutine all in the same self-contained Flow instance. The callback is registered only while the flow is being collected. Cancellation of the flow automatically propagates into closing the channel and deregistering the callback. You just have to provide the callback-deregistering code once.
You should look at Channel as a lower-level primitive that Flow uses in its implementation. Consider working with it directly only after you realize Flow doesn’t fit your requirements.