I'm only seeing purple blocks on black background at the menu (like you're missing material or shader) with the "experimental" build and the "old" build I'm seeing a small purple cube at an odd angle....
same OS (Void Linux) and similar CPU only difference really is the GeForce GT 640
I'll experiment with some of the Mesa environment variables and let you know if I get any joy!
I'm running Ubuntu Gnome 16.04 with Nvidia Quadro FX 880M/PCIe/SSE2, and it worked perfectly. Only have to turn down the graphics detail level when flying the maps with trees as my GPU can't handle it.