Quality of security aside, I'd be curious which encrypted messaging apps have the highest quantity of (encrypted—some support unencrypted, also, as Messages doe

Quality of security aside, I'd be curious which encrypted messaging apps have the highest quantity of (encrypted—some support unencrypted, also, as Messages does) messages flowing through them in a given day—for, say, US users, as that's the jurisdiction of the government whose motives are being questioned, so seems the most relevant. One can imagine a case of a particular app drawing law enforcement's and/or intelligence services' ire not because it's the best, but because they're seeing a lot more conversations they wish they could read, but can't (easily), going over that channel than any other single one.