This upscaler is not mine, all the credit goes to: KIM2091

Official WIKI page: openmodeldb

License of use it: CC-BY-NC-SA-4.0

HOW TO INSTALL:

Copy the file 4x-UltraMix_Smooth.safetensors inside the folder: stable-diffusion/models/ESRGAN or ComfyUI/models/upscale_models

Restart/Reload you Stable Diffusion instance

The upscaler should be visible for hi-res and extras tabs