I read it, and it was shared within the FSFE previously. Currently both XMPP and Matrix are available, but not bridged. Personally I think XMPP is fine for the FSFE, but Matrix is growing in adoption in the larger free software community, and thus might be a lower barrier of entry compared to XMPP. I see positive and negative sides for both.
In recent years the XMPP setup of FSFE has increased quite a bit. The most important feature to me was the caching of messages, something that I feel is lacking in say IRC. Both Matrix and XMPP now offer this message caching, and offer methods for end-to-end encryption, so the choice between both of them to me is more of a nuance.
Dr. Trigon, what is the main concern you have with Matrix for bringing this up?
Best, Nico