It's likely there is a more proper way of doing it, not needing to uninstall, but I just lost my patience at this point.
Maybe still needs the non-GTK versions, a "neutral" one and a kde and a qt5 one, I can't really tell. I was about to uninstall them all, but occurred to me to try to uninstall just the gtk one, and voilá, I had kdialog on chrome-based-browsers again.
Why can't things be set by text files or environment variables with sane standards?...