Whitemane Lion

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

• WWizards of the Coast2022-12-08
  Official Ruling
  Whitemane Lion's ability doesn't target any creature, therefore no player may take actions between the time you choose the creature to return and the time you return it.
• WWizards of the Coast2022-12-08
  Official Ruling
  You may return Whitemane Lion itself to its owner's hand as its triggered ability resolves. If you don't control any other creature, you must return it.

Rulings via Scryfall