SONIC FRONTIERS (PS5) Playthrough: Chaos Island (36th Segment) Almost Figured It out
So the location of the badnik robot seems to hint where the way to the deserted island section is. There's A decent opening in the ground there leading to an underground area, that might be it. Sonic Frontiers, PlayStation 5, Chaos Island, 36th, segment, exploration, continues, Starfall Islands.