I just hopped back online to host against a bot and the summon mechanic of Formula Synchron off of the skill Shooting Star Road is working as expected.
The Skill Shooting Star Road still shows invalid when using the Duel Links latest ban list, however it is within Duel Links now as a valid skill and still appears as green, unlike the other skills that appear as blue. When playing under Unlimited and hosting it is able to be used.
The same is true of Demon’s Resonance. It too works as expected outside of that from my testing.