Current tigervnc has broken deps in it's modules subpackage:
DEBUG util.py:439: - nothing provides xserver-abi(videodrv-23) >= 0 needed by tigervnc-server-module-1.8.0-7.fc28.i686
DEBUG util.py:439: - nothing provides xserver-abi(videodrv-23) >= 0 needed by tigervnc-server-module-1.8.0-7.fc28.x86_64
So it needs a rebuild against the new 1.20 X server. A simple rebuild fails:
We will need a rebuild soon, or will have to untag the new X server so we can get rawhide composes again. ;(
I fixed this already an hour ago.