Rocket.Chat/server/startup/migrations/v012.js

RocketChat.Migrations.add({
	version: 12,
	up() {
		// Set oldest user as admin, if none exists yet
		const admin = RocketChat.models.Users.findOneAdmin(true, {
			fields: {
				_id: 1
			}
		});

		if (!admin) {
			// get oldest user
			const oldestUser = RocketChat.models.Users.findOne({}, {
				fields: {
					username: 1
				},
				sort: {
					createdAt: 1
				}
			});

			if (oldestUser) {
				Meteor.users.update({
					_id: oldestUser._id
				}, {
					$set: {
						admin: true
					}
				});

				return console.log(`Set ${ oldestUser.username } as admin for being the oldest user`);
			}
		}
	}
});