Great, thanks David!
It works here, though I encountered a problem with a dialog box popping up saying it failed to update the filters (it seems to try updating automatically by itself?) and a crash after finishing applying a filter (Illustration look).
I also got a message the first time I loaded the Qt plugin, asking if I wanted to import faves. I answered “yes”, but it imported only 4 faves (in duplicate in fact) out of 10+ I had set up from the Gtk plugin. The good news is that it asked me to import the faves only the first time.
So far it works as fast as the Gtk version on my system (not faster, not slower… though the Gtk version was self compiled using -march=native).