I'm currently playing FTB Utimate with Shader. I have a ryzen 5, rtx 2060 and 16gb ram. If I play without a shader I have a stable 130-150fps but as soon as I put in a shader, no matter which one, I only have 60fps and they often drop down to 30fps which frustrates me… Regardless of whether I'm with a low shader or a high end shader gamble it always stays the same fps. I do not check there's probably another reason why it could lag or is it due to my hardware? In the in-game settings, I have already reduced everything, unfortunately, does not bring much.
It is certainly not due to your hardware. Search times on Google for Badlionclient then you would have to come across a program for Minecraft and that ensures that you don't get any more lags.
The client just preinstalled optifine or not? I've already installed Optifine
What kind of shader do you have?
I've tried almost every one, both serious and chocapic low and and and the shader pack is definitely not because the fps remains the same regardless of which one I have inside
Then it may be due to the modpack. Uninstall the mod from Minecraft and add your shader again. Then look whether it works lag-free. Then it's the Modpack