Frondland Felidar

• WOTC Official Reminder Textofficial rules
  Vigilance — Attacking doesn't cause this creature to tap.

• WWizards of the Coast2020-04-17
  Official Ruling
  Once you’ve activated the ability granted by Frondland Felidar, causing the creature to lose that ability (such as by removing Frondland Felidar from the battlefield) won’t affect the ability on the stack.
• WWizards of the Coast2020-04-17
  Official Ruling
  Frondland Felidar’s last ability applies to itself as long as it still has vigilance.
• WWizards of the Coast2020-04-17
  Official Ruling
  You can activate the ability granted by Frondland Felidar after attacking but before blockers are chosen.
• WWizards of the Coast2020-04-17
  Official Ruling
  Tapping an attacking creature doesn’t remove it from combat.

Rulings via Scryfall