µBlock and µMatrix are parallel offshoots of gorhill's earlier HTTP Switchboard. They're refactored forms of HTTP Switchboard, where each extension focuses on different forms of blocking (µBlock for pattern-based filtering, µMatrix for matrix-based filtering).

See:

https://github.com/gorhill/uMatrix/wiki/Changes-from-HTTP-Sw...

https://github.com/gorhill/uMatrix/wiki/Using-%C2%B5Block-wi...