Portal Manipulator

• WOTC Official Reminder Textofficial rules
  Flash — You may cast this spell any time you could cast an instant.

• WWizards of the Coast2024-02-02
  Official Ruling
  Portal Manipulator's triggered ability doesn't cause "whenever this creature attacks" abilities to trigger.
• WWizards of the Coast2024-02-02
  Official Ruling
  If an ability targets something controlled by the "defending player" of an attacking creature and the defending player for that creature changes before that ability resolves, the ability won't resolve because its target has become illegal.
• WWizards of the Coast2024-02-02
  Official Ruling
  Once Portal Manipulator's triggered ability resolves, the target attacking creatures are still considered to have attacked the player, planeswalker, or battle they were initially declared as attacking, but they are now attacking the target player.
• WWizards of the Coast2024-02-02
  Official Ruling
  Portal Manipulator's triggered ability ignores all requirements, restrictions, and costs associated with attacking.
• WWizards of the Coast2024-02-02
  Official Ruling
  You may cast Portal Manipulator outside of a declare attackers step. If Portal Manipulator enters the battlefield outside of a declare attackers step, its ability simply doesn't trigger.

Rulings via Scryfall