Since this is not the current "stable" main release on the official website (reshade.me), you will typically find this version in two places:
Often, version 5.9.1 is distributed as a manual zip file for compatibility with specific presets (like those for Elder Scrolls Online ). reshade 5.9 1
“Fixed depth buffer detection for D3D10/11 games using certain deferred rendering paths. Improved add-on API for depth access.” Since this is not the current "stable" main
Version 5.9.1 is notable because it belongs to the generation that introduced updates and improved support for newer DirectX versions, making it highly stable for many older and current titles. reshade 5.9 1