Luxchat4Gov and Luxchat for the general public and businesses are interoperable national instant messaging services, based on the Matrix technology.
Matrix is an open standardized protocol for instant communication, developed by a large, mainly European community, and supported by a foundation, The matrix.org Foundation, guaranteeing the sustainability of the key principles and foundations of the Matrix technology.
They are not, see this comment : https://feddit.org/post/12874767/6782226
Thank you for your elaborate reply!