Civilization: Beyond Earth isn't exclusive to Mantle, with the API on Windows just being supported on newer Catalyst drivers with newer GCN GPUs and NVIDIA not showing any signs of committing to Mantle support. NVIDIA and others (including AMD) are instead more focused on reducing the OpenGL driver overhead and improvements to Direct3D. While some are getting their hopes up that Civilization: Beyond Earth will introduce Mantle Linux support by AMD's Catalyst Linux driver, don't get your hopes up as it doesn't look that way.
We've been wondering about Mantle on Linux going back to its premiere last year but there's been no commitment to Linux support. Last month when I was out at GDC 2014, I was told by AMD representatives that they're still looking at the feasibility of Mantle on Linux.
AMD's response was that they would like to see Mantle on Linux but it comes down to a resource issue. They haven't yet started writing any Linux Mantle driver code and are more focused on their new, more-open driver strategy and they have very limited Linux engineering resources. It would be nice to see Mantle on Linux, but at the end of the day it probably won't happen. There's also the matter of whether Mantle will even be around for the long-term with OpenGL and Direct3D receiving improvements to enhance the performance of these existing, cross-vendor 3D rendering APIs.
Further making it look like there will be no Mantle Linux support for Civilization: Beyond Earth is apparent confirmation from Michael Marks, the development director at Aspyr Media and founder of Strega Games. Marks also has a history with AMD and NVIDIA. He posted on Twitter this weekend that there will be no Mantle support coming to Apple OS X nor will there be Mantle for SteamOS (Linux) but that Graham Sellers at AMD will be working to make sure Beyond Earth runs on AMD Linux configurations.
Let's just hope that by the end of the year Civilization: Beyond Earth will be able to render bug-free and with decent performance on AMD's Catalyst OpenGL driver while Linux gamers will be real lucky if it also manages to run fine on the open-source R600g/RadeonSI Gallium3D drivers.
Update: AMD has said they are still evaluating future platforms for Mantle. So Linux support isn't ruled out completely, but it's basically the same statement I reported last month from GDC that they're still in the evaluation stage.