Released in late 2019, version 1.5.97.0 was the final major update for Skyrim Special Edition before the transition to the in November 2021. The shift to v1.6.x broke many essential Skyrim Script Extender (SKSE) plugins, leading a large portion of the player base to "freeze" their game at 1.5.97.0.
Quick and brainless guide to downgrading Skyrim SE to 1.5.97
Certain high-level tools, such as the No Grass In Objects (NGIO) mod required for generating complex grass LODs, are natively designed for this version. How to Achieve and Maintain v1.5.97.0
Many veteran modders have moved on from the scene, leaving highly technical .dll plugins only compatible with the 1.5.97.0 executable.
This version was the active standard for nearly two years, allowing mod authors to refine their work without fear of sudden game updates breaking core mechanics.