In order for you to play Tropico 6 on Linux with minimal graphics settings, your computer must meet the following requirements
Operating System:
Ubuntu 16.04.3 LTS + SteamOS (latest)
Processor (CPU):
AMD or Intel, 3 GHz (AMD A10 7850K, Intel i3-2000)
Memory (RAM):
8 GB RAM
Graphics Card:
AMD/NVIDIA dedicated GPU, 2GB dedicated VRAM (Radeon HD 7870, Geforce GTX 750)