The End Portals texture is replaced with that of the sky, only seems to happen when using the shader.

• Iris, Minecraft v1.21
• Minature Shader v2.13.2

https://modrinth.com/shader/better-end-portal-shader
I also beleive this may have what you need, it specifies you have permission to use it as long as u credit it

It's not really using the sky texture, the usual effects just aren't there. I've known this for a while now, but it just doesn't seem worth it to fix it. I'll keep it open regardless, if someone else wants to fix it.

ah I see, got it

though I have found this post from a while ago, which seems to mention problems with optifine rendering the portal with shaders (though im using iris it may be an issue?) maybe if there's a way to remake the portal's textures it may work (I beleive complementary reimagined does this quite well but it may be out of scope)