Can you play a reaction card at the end of turn if no triggers are active?

Ruling: No, you cannot play a reaction at end of turn if there are no end of turn triggers. You can only play reactions when you get priority, which happens in showdowns or when a spell/ability is on the chain.

Nuances:

• You can play reactions in response to end of turn triggers like Dazzling Aurora or Annie Legend's ability to ready runes
• Some keywords are abilities you can react to (like Deathknell and Equip which are activated abilities) while others are passive and cannot be reacted to (like Shield and Assault)
• Equip being an activated ability that can be responded to is not widely apparent to players