Example, WhatsApp, use the whole 25 character profile name limit:
Bob Moved To Signal.org
Alice MovedTo Signal.org
CharlieMovedTo Signal.org
Say Signal.org, not Signal, so they see it is an app.
Use your about section too.
Same on Discord, Steam, Instagram, everywhere.
Also, I shortened it to just “[Name] is on Signal.org”. People get the same idea, and it saves some space for long names and/or is more often read as it is shorter :)
Good idea!