My setup:
MC 1.21.10, Fabric 0.18.1, Iris 1.9.6
Os: arch
Shader: IterationT 3.2.0
Error
"lines: lines: 0:1(10): error: the compatibility profile is not supported"
Other shaders like bsl and photon worked fine, its the RT shaders that are borked
Since it was not working on linux, i played it on windows and it worked fine using same shaders, mc version and iris version. I have a feeling it's related to drivers but I'm not sure.