2021-11-19 : All attackers are chosen at once. You can't attack with Militia Rallier, untap a tapped creature, then attack with that creature.

2021-11-19 : Untapping an attacking creature doesn't remove it from combat.

2021-11-19 : You may target an untapped creature with this ability. For example, if all of your creatures have vigilance, you aren't forced to untap an opponent's creature.