There is a new minor version of MAT2: 0.13.1, without major fixes, but with cleaner code and some minor improvements. The main change is that the Nautilus extension is no more: Nautilus 43 is slow and I don't like it, so my motivation/incentive to port the mat2 extension to its new API is non-existent. Moreover, Metadata Cleaner is a stellar alternative: pretty, simple, accessible, translated, … it's glorious.
As usual, if you know some python help is welcome.