Archelos, Lagoon Mystic

• WWizards of the Coast2020-11-10
  Official Ruling
  Archelos's abilities don't apply to itself as it enters the battlefield, nor do they apply to any permanents entering the battlefield at the same time.
• WWizards of the Coast2020-11-10
  Official Ruling
  If more than one Archelos is on the battlefield, the controller of an entering permanent chooses how to order the replacement effects.
• WWizards of the Coast2020-11-10
  Official Ruling
  If another replacement effect says that a permanent enters the battlefield tapped while Archelos is untapped, the entering permanent's controller chooses whether the permanent enters tapped or untapped. If a permanent is simply put onto the battlefield tapped without a replacement effect being applied, it always enters untapped if Archelos is untapped.

Rulings via Scryfall