This upscaler is not mine, all the credit goes to: N00MKRAD

Official WIKI page: openmodeldb

License of use it: WTFPL

HOW TO INSTALL:

Rename the file from: nmkdSiaxCX_200k.pt to 4x_NMKD-Siax_200k.pth

Copy the file 4x_NMKD-Siax_200k.pth inside the folder: stable-diffusion/models/ESRGAN

Restart/Reload you Stable Diffusion instance

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