This is unfortunately completely wrong, since you can learn from the homepage of matrix very own client Element, that its supported an trusted by a whole bunch of NATO Armys, including the US of course...

I don't mean by that you shouldnt use matrix, but arguing against signal with matrix is, in so many means, hilarious.

The arguable, but professional cryptographer soatok discribes from a mathematical/cryptographical point of view, what it needs to be a Signal competitor, where matrix (and others) dont catch up (unfortunately)