https://bugzilla.redhat.com/show_bug.cgi?id=1724109
See the crickets chirping. A year ago in February the maintainer said that he managed to get qt5-webengine "built on ppc64le", and would start working on it... Then nothing.
Sounds like the maintainer just coincidentally uses a low-tier supported system that is having compilation issues with webengine and he can't get a build environment set up to test it on the primary arches?