Minecraft shader 1.15.2?

How do I get a shader for Minecraft version 1.15.2?

The shader is grayed out with the current Optifine version (pre 9).

But I was told that shaders still work with the pre 2 version. So how can I get a shader / How can I download the pre 2 version?

If you download optifine you should be able to choose the version. During my research I did not find an optifine for 1.15.