For example, on WhatsApp, use the whole 25 character limit for profile name. Examples:
Bob Moved To Signal.org
Alice MovedTo Signal.org
CharlieMovedTo Signal.org
Say Signal.org, not Signal, because they won’t know it’s an app.
Use your about section too. Same on Discord, Steam, Instagram, etc.
I’ve started to get much more interested in SimpleX as the database management is much easier and disappearing messages exist and while that is not a privacy function it is a great database management function to automatically have messages removed