There isn’t a lot to say about this. Ardour 2.X had what one expert in the field called “the best synchronization behaviour with MTC of any DAW I’ve ever seen”. Ardour 3.0 has some improvements that help when using certain MTC-transmitting devices as the master, and also formalize the synchronization design a bit more. Torben Hohn was largely responsible for this code.
We also improved the way that the sync source is selected (whether its MTC or something else) and displayed, and how timecode options are displayed, which is described over here