Principia Matrix space
The Principia Matrix space has unfortunately been shut down due to issues with the Matrix bridge service we used leaving it in an unusable state for most of the time. Because of the lack of interest in setting up our own bridge for the project and there being no activity in the space for over a year it was eventually shut down.
If there is interest in a Matrix space for Principia then it can be brought back. If you would like to offer to host a bridge please reach out!