The specific version you mentioned (v1.2.9.38256) is a stable build that includes various quality-of-life updates and bug fixes from the developers at TaleWorlds Entertainment .
Mount & Blade II: Bannerlord v1.2.9.38256 - Experience the Ultimate Sandbox Warfare (Repack) Mount and Blade II Bannerlord v1.2.9.38256-Repack
Recruit companions to fill specific roles in your clan, eventually leading their own parties or managing settlements. The specific version you mentioned (v1