In old GTK3 applications we sometimes used g_signal_handler_block() to temporary block user input for Widgets, e.g. to block temporary mouse clicks in a drawing area. This worked for the old GdkEvents.
g_signal_handler_block() didn’t do anything to events: it blocks a signal emission.
Since GtkGestures and event controllers emit signals, you can do precisely the same thing; the object is the only thing that changes from the widget to the event controller.
Unless, of course, you’re trying to block a signal on an existing widget that you don’t control/did not write; in that case, blocking signal emission was already a bad idea with GTK3. The typical solution is to have a boolean flag somewhere that you check in a signal handler. Of course, that still assumes you’re blocking a signal handler you’re adding yourself with g_signal_connect().