Thank you very much for your comment. It is a very valuable and important note for the subject and community as this is a super important aspect of image SR. We refer to this topic under the Unsupervised SR section (8) but did not have the space to go into more detail, which doesn't mean it doesn't deserve attention. We referenced another survey by Liu et al. (“Blind image superresolution: A survey and beyond", https://arxiv.org/abs/2107.03055) from 2022 to fill this gap (also mentions KernelGAN and related methods), which we find is an informative source for blind SR in general.