Thanks for the fast reply!
However, my output is the following:
$ ldd /opt/svp/extensions/libPythonQt.so
linux-vdso.so.1 (0x00007ffea37e4000)
libpython3.4m.so.1.0 => not found
libQt5Widgets.so.5 => /usr/lib/libQt5Widgets.so.5 (0x00007f5da4358000)
libQt5Gui.so.5 => /usr/lib/libQt5Gui.so.5 (0x00007f5da3c1c000)
libQt5Core.so.5 => /usr/lib/libQt5Core.so.5 (0x00007f5da3545000)
......
for some reason he expects libpython3.4m.so.1.0 instead of 3.5.
After a quick and dirty fix via
ln -s /usr/lib/libpython3.5m.so.1.0 /usr/lib/libpython3.4m.so.1.0
The extension showed up as expected.
Again, thanks for the quick and helpful support!