NATO is testing out this decentralized messenger for communications between member nations
Briefly

"We are allowed to experiment, and to explore," says Franssen. The proof of concept is being limited to around 700 users across NATO at present before a wider roll-out.
Member states, including Germany, France, Poland, Austria, Sweden, the U.K. and U.S. have all individually adopted Matrix because of the system's adaptability and security.
They now have a community of interest internally within NATO for coordinating these very many disparate things, making sure they can directly talk to one another.
Many of NATO member states actually already use Matrix tech in their work. Those nations are interested in the tech because it's open-source and encrypted.
Read at Fast Company
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