RHEL 7.5 updates qt5 from 5.6.2 to 5.9.2, leaving some Qt-related packages in EPEL uninstallable. If already installed, the entire system upgrade can get blocked.
As far as qt-creator is concerned, these dependencies seem relevant:
qt-creator-4.1.0-3.el7.x86_64 requires qt5-qtbase(x86-64) = 5.6.2
qt5-qtwebkit-5.6.2-1.el7.x86_64 requires qt5-qtbase(x86-64) = 5.6.2
qt5-qtwebkit-5.6.2-1.el7.x86_64 requires qt5-qtdeclarative(x86-64) = 5.6.2
In addition there's at least this, but there are probably more.
qt5-qtquick1-5.6.2-1.64faeb0git.el7.x86_64 requires qt5-qtbase(x86-64) = 5.6.2
It needs to be recompiled against new libs, you can send an email to the people listed here ->
A new qt5-qtwebkit is already available in epel-testing, see bug 1572156. Same for qt5-qtquick1, bug 1576820.
The qt-creator issue still remains, though.
*** Bug 1577741 has been marked as a duplicate of this bug. ***
This isn't current anymore.