Mercutio
Fatwah on Western Digital
Do the T&C of the software platform indicate the means of communication? I would think that you want something with records for evidence.
This is mostly for voice communications.
Games may or may not be cross platform. Communication services might be cross platform but only in a single game, platform wide but only for a specific console, or rely on a central service. The most common central service these days is just the one that happens to be something I don't like for a bunch of reasons that have nothing to do with voice communication.