Upscalers

https://upscale.wiki/wiki/Model_Database

https://upscale.wiki/wiki/Official_Research_Models

https://huggingface.co/uwg/upscaler/tree/main - the most comprehensive repo with all the upscalers

ESRGAN

https://huggingface.co/uwg/upscaler/tree/main/ESRGAN

4x_NMKD-Siax_200k

cd /workspace/stable-diffusion-webui/models/ESRGAN
wget https://huggingface.co/uwg/upscaler/resolve/main/ESRGAN/4x_NMKD-Siax_200k.pth

4x_foolhardy_Remacri

cd /workspace/stable-diffusion-webui/models/ESRGAN
wget https://huggingface.co/FacehugmanIII/4x_foolhardy_Remacri/resolve/main/4x_foolhardy_Remacri.pth

8x_NMKD-Superscale_150000_G

My go to for hires fix and also 8x upscale in ComfyUI

cd /workspace/stable-diffusion-webui/models/ESRGAN
wget https://huggingface.co/uwg/upscaler/resolve/main/ESRGAN/8x_NMKD-Superscale_150000_G.pth