> Electron was not considered Free Software by the Free Software Foundation.

That is not true. The link shows that a volunteer on the free software directory labeled it as nonfree at one point and later it was changed. However, the FSF did find that matrix in practice leads users to run nonfree software: https://www.fsf.org/news/fsf-and-gnu-move-official-irc-chann... "Doing so would create the unacceptable situation of encouraging a large number of users to run nonfree software in the form of nonfree JavaScript, which is used by the flagship Matrix.org server to authenticate users."