Is there a way to make the “Auto-generate Preview Surface Shaders” option in the Material Library default to off , instead of having to disable it manually? I don’t want to wait for textures to keep loading, as it’s very slow.

You can turn it off, and set it as default node value on the cog top right.

Can this be configured via environment variables, for example: set "Auto_Generate_Preview_Surface_Shaders=0"?