This upscaler is not mine, all the credit goes to: XINNTAO
Official WIKI page: openmodeldb
License of use it: BSD-3-Clause
HOW TO INSTALL:
Rename the file from: realesrGeneralWDNX4_v3.pt
to realesr-general-wdn-x4v3.pth
Copy the file realesr-general-wdn-x4v3.pth
inside the folder: stable-diffusion/models/RealESRGAN
Restart/Reload you Stable Diffusion instance
The upscaler should be visible for hi-res and extras tabs