I'm currently building qpdf-9.0.1 and cups-filters-1.25.0 for Leap 15.0 and 15.1 on my home project https://build.opensuse.org/project/show/home:letsfindaway. I just copypac'ed the packages from Leap 15.2 and they built without causing any further dependency. As soon as they are published in the repository I will test them and come back here to inform you about the results. Perhaps backporting these packages from 15.2 could be an easy way to solve the problem.