Feral Interactive did an amazing job with this port. And AMD has done an incredible job with their Radeon and RadeonSI drivers. Not only does it fully support the latest Mesa3D driver (11.2), but Fglrx isn’t even officially supported due to a rendering issue.
Tomb Raider has a built-in tool that I used for the benchmark. I tested my Radeon R7 360 card and my A10 7850k APU (integrated graphics). The R7 360 averaged a whopping 60 fps! That’s incredible feat for the open source driver! The 7850k only achieved about 27 fps, but the 7850k is way believe minimum specs for the game.