FTL in SR does not break causality. Some FTL travel is "allowed", at least causality allows it. A natural model for SR + FTL that is consistent with causality, is that SR is an emerging phenomenon / effective theory over a Galilean space time. If you can, say, send information in the Galilean space time with arbitrary velocity, then you can send information FTL, but causality is total cool with it.
It is also possible, that you can move with arbitrary speeds in this Galilean spacetime (but I believe we haven't observed anything in the universe that moves FTL).
However, arbitrary FTL would mean you can send information from anywhere and anywhen to anywhere and anywhen, which breaks causality.
It is also possible, that you can move with arbitrary speeds in this Galilean spacetime (but I believe we haven't observed anything in the universe that moves FTL).
However, arbitrary FTL would mean you can send information from anywhere and anywhen to anywhere and anywhen, which breaks causality.