Shining Armor

Flash
When Shining Armor enters, attach it to target Knight you control.
Equipped creature gets +0/+2 and has vigilance.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Jumpstart 2022

Flash
When Shining Armor enters the battlefield, attach it to target Knight you control.
Equipped creature gets +0/+2 and has vigilance.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

The List

Throne of Eldraine

Gaining vigilance any time after the moment you choose to attack with a creature won't cause it to become untapped.

If there are no Knights to attach Shining Armor to when it enters the battlefield, it simply remains unattached.