In the original Sun/Moon, you could battle each of these trial captains after defeating the kahuna of the island their trial is on. Can you battle these people in such a way in this game, or do I have to wait until Mina's trial in order to battle them all again? I've tried to find Ilima, but he wasn't in his room, so I'm not sure if this is available in these versions.
You can battle them after beating the Elite Four and champion. source:https://www.serebii.net/ultrasunultramoon/trialcaptains.shtml