Which external voice-chat app is mentioned in Wikipedia’s Among Us gameplay section? It is Discord.
Among Us includes in-game text communication, but its gameplay section also names Discord as an example of an external voice-chat application. Players commonly use voice chat during meetings to discuss suspicious movement, alibis, task locations, and possible Impostor behavior.
Discord became strongly associated with Among Us because the game’s social-deduction format benefits from rapid spoken conversation. Friends can talk between meetings, though many groups impose “no talking” rules during active play so that dead players cannot reveal information and living players cannot accidentally share knowledge outside meetings.
The reference to Discord does not mean it is required to play. Among Us supports in-game text chat and, depending on the platform, other communication features. Discord is simply the named external example in the cited gameplay description. TeamSpeak, Zoom, and Skype are plausible voice or video-chat services, but they are not the canonical answer to this wording. Discord also became popular for communities, game servers, moderation, and voice channels beyond Among Us.