[neiljohnson]

Signal and WhatsApp only address the personal messaging usecase, whereas the letter is also talking about wider chat services like Teams.

More to the point, even with e2ee, there is still communication metadata that is leaving your network for a third-party service. In a defense context, you would almost certainly prefer that the data does not leave your network unnecessarily.

In terms of Matrix usability and performance, Matrix 2.0 (https://matrix.org/blog/2024/10/29/matrix-2.0-is-here/) represents a huge step forward and can be used today with compatible clients such as Element X (https://element.io/blog/deep-dive-into-element-x/)