I haven't tried building yet but it's looking pretty good so far.
One thing I noticed, you have some lines like these in the various ports,
CONFIGURE_ENV += Qt5Widgets_DIR=${LOCALBASE}/lib/qt5/cmake
CONFIGURE_ENV += Qt5LinguistTools_DIR=${LOCALBASE}/lib/qt5/cmake
CONFIGURE_ENV += Qt5X11Extras_DIR=${LOCALBASE}/lib/qt5/cmake
With qt5 cmake-based ports it's intended that MODULES=x11/qt5 is used,
which sets these up automatically.
> I made a mailing-list in googlegroups as the KDE Porting Team did.
Not a major objection but tbh I'm not a huge fan of using a mailing list
as a MAINTAINER address.
> - Someone writing better DESCRs and README?
>From a quick read through I think they're good enough to use, could
be tweaked a bit but it would be simpler to do this by sending diffs
after it's imported.