When I enabled texture packs with PBR in SEUS GFME this happened (screenshots below) and I guess this is again an Iris bug in SEUS GFME support.
Minecraft 1.21.4
Fabric Loader 0.16.9
Iris 1.8.4
Sodium 0.6.6
Shader pack: SEUS GFME v17.0
Please fix it!