The NVIDIA GPUs Delivering The Best Performance Per Watt & Per Dollar For Linux Gamers
SuperTuxKart's OpenGL 3 renderer is still in need of more performance tuning... But anyhow, the GTX 970 and higher can run it smoothly at 4K.
The GeForce GTX 960/970 is sure looking like a nice sweet spot so far for Linux gamers in being efficient yet offering the best value and being certainly playable at 1080p and generally playable with current Linux games at 4K.
Tesseract is certainly playable at 4K.