Can a player play a reaction at the end of their opponent's turn when the opponent passes priority without starting a chain?

Ruling: You do not get priority by default on your opponent's turn unless they start a chain (via starting a showdown, finalizing a spell, activating or triggering an ability, etc).

Nuances:

• Simply playing a unit does not give the opponent an opportunity to play a reaction unless something is triggered
• You cannot play a reaction like Consult the Past in response to an opponent passing their turn if no chain was started