In order for you to play Mount & Blade: Warband on Linux with minimal graphics settings, your computer must meet the following requirements
Minimum:
Operating System:
Ubuntu 16.04 LTS, Steam OS
Processor (CPU):
Intel Core Duo 2.0 GHz or AMD Athlon 64 X2 3600+
Memory (RAM):
1 GB RAM
Graphics Card:
NVIDIA GeForce 6600GT / ATi Radeon 2400 or better
Hard Drive:
1 GB available space
Sound:
Standard audio