Worth pointing out that some of the largest proponents of Matrix today are governments and civic institutions. The federated nature and ability to self host are really important to them.

The French government's installation has been in the public domain for sometime (https://matrix.org/blog/2018/04/26/matrix-and-riot-confirmed...)

More recently the German Education authority has announced that it will roll out a 500K user installation - this is the world’s largest-ever single contract for a collaborative software service (https://sifted.eu/articles/element-germany-deal/)