After installing a curseforge modpack, click on the 3 dots - Profile Options - and checkmark "Allow content management for this profile"
Then go to Content and click on the Shaders tab - add some shaderpacks there
To load shaders, make sure the modpack is using Embeddium and Oculus (alternative for Optifine)
A NeoForge or Fabric modpack is using Sodium and Iris
With adding Embeddium, the mod Rubidium is automatically added as dependency - this causes a duplicate mod error
So after adding Embeddium, make sure you remove Rubidium from the modlist