IOW, I was right and it was a distro problem (or maybe a config problem that got fixed with a reboot).
22:46.57 <QKO> Lam: the update fixed it it seems o_O
22:48.45 <QKO> (x did not get upgraded)
22:51.04 <Lam> what was updated then?
23:03.27 <QKO> Lam: nvidia drivers and a bunch of unrelated crap
So now the remaining question is: is there really a plan to obsolete the DGA mouse extension and if so, when is it scheduled to happen? X Input is a horribly complicated API that offers absolutely no advantage to QL players, so again: I don't see any reason to migrate over, unless forced.