Have a look at Unity Libre Fracture, a free and open-source fracture system developed for Unity by Dmitry Senyushkin. The system uses NVIDIA Blast wrapper for Unity as a base. As for concave meshes, it uses VHACD (Volumetric Hierarchical Approximate Convex Decomposition).
The developer also plans to improve and add a number of things:
Fix physical stability issue, probably related to the centers of masses (can be noticed on round objects like spheres when fractured)
Distribute mass along chunks with taking their size into account
If FractureObject had any joints attached and it was then fractured, make corresponding joints at the chunk(s) to the same connected body