Installing this mod causes all mobs to have extremely weird textures, they are glitching. A good description would be the look of that ai generated Minecraft. Specs: Qualcomm 8 elite, Adreno 830, 16/512gb storage. I noticed the same behavior with Iris. All other mods used are in the screenshot below.

What OS / Device are you running this on?

i am using the oneplus pad 3 on android 15, for the launcher it's pojav launcher glow worm. I was playing 1.21.5 now for a while and didn't experience this, so idk what went wrong. The launcher is unofficial, yes, but the game runs no different than windows, macs or linux and all mods are compatible.

Running ImmediatelyFast on mobile devices is not officially supported. This is an issue with the OpenGL translation layer Pojav is using. You should report this issue to them, so they can fix their OpenGL translation layer.