Ah, vorta build is actually broken due to the QT updates. I had built before I pulled these QT updates. I think the same as in https://issues.guix.gnu.org/56864 and reportedly fixed in https://issues.guix.gnu.org/56771#39
I'm not sure the fix here, as Vorta uses the python-build-system and then adds the qt-wrap phase explicitly. I tried adding a qtbase input but that didn't help.
Will have to investigate later unless someone knows the quick fix.