Docs: need to improve documentation how to receive unhandled + dead letters

[Aaronontheweb]

Please describe what you are trying to understand
Original issue reported by user here at SO: https://stackoverflow.com/questions/69656719/akka-net-1-4-dead-letter-handler-eventstream-subscribe

Just because it cost me a few hours, I'd like to share the following insight, may it be interesting for someone: If we want to handle dead letters by ourselves, the akka.net documentation (https://getakka.net/articles/utilities/event-bus.html) says we should use

"system.EventStream.Subscribe(deadletterWatchActorRef, typeof(DeadLetter));" 

This is only partly true - yes, this catches those messages which are strictly "dead letters", those whose recipient is currently dead. But it does not catch the unhandled messages and the dropped ones. If you want that (and I'm pretty sure that 99% of the use cases don't want to finely differentiate between unprocessed, dropped and really dead letters), you have to use "AllDeadLetters" instead of "DeadLetters", so the proper call is

system.EventStream.Subscribe(deadletterWatchActorRef, typeof(AllDeadLetters));

Which pages have you looked at?

1. https://getakka.net/articles/utilities/event-bus.html

What did these pages not make clear?
Doesn't distinguish between dead letters and unhandled messages, and doesn't explain how to capture both.

How can we do it better?
Go into detail on what the different types of unhandled messages mean and explain how to subscribe to all of them via the EventStream. Might want to make this information more easily discoverable in the navigation too.