I am the author and maintainer of the matrix package:

For several reasons, mostly time related, I can't give this package the attention it deserves. GitHub issues are not being properly taken care of, and development stopped long time ago.

Instead of leaving the package in this state, I thought about giving maintenance powers to anybody interested in continuing this work, or even change its direction in any (reasonable) way. I know the package has some users, so maybe any of you wants to do it. Otherwise, I guess I should try to allocate some time to at least fix some of the issues posted in GitHub. Meanwhile, sorry for the long waiting time that I have imposed on the users of this package that have reported problems or submitted PRs.

King regards,

Daniel Díaz.