I tried this a couple years ago with Netlify and Hugo targeting 1x, 2x and 3x sized images. The processing time is too slow with more than around 500 images, resulting in build timeouts.
I switched to checking in the alternate image sizes and using a hugo image render hook to check for the existence of the alternative images to generate the appropriate srcset.
I switched to checking in the alternate image sizes and using a hugo image render hook to check for the existence of the alternative images to generate the appropriate srcset.