Many "DLL-based" mods (like Address Library or Engine Fixes) required updates. If you are downloading the non-Steam version for modding, ensure you match your SKSE version specifically to the GOG or Epic build numbers, as they are not identical to the Steam build. Installation for Non-Steam Versions
Update 1.9 was the final major patch for the original 32-bit version of Skyrim. It addressed hundreds of bugs and introduced features that are now considered baseline: skyrim+update+19+download+non+steam+exclusive