Tests with the provided images: * debian-9.0+HACK-amd64-NETINST-1-with-provides.iso does the trick * tasksel show both LXDE and LXQt so this point is fixed * installation of both LXDE and LXQt went well, LXQt perfect, LXDE picked up lxqt-policykit somehow, possible not related to tasksel. Should be a different issue, will file a bug if analyzed it * with the unpatched tasksel LXDE picked up more or less LXQt packages, esp common and session - this behaviour is gone.
I would give it a go, thank you KiBi
