Euro 2020 postponed to 2021: What happens now?

Euro 2020 has now officially been postponed to 2021 by UEFA - but what happens now? What will the tournament look like? What happens to the Champions League and Europa League?

Euro 2020 postponed to 2021: What happens now?
Euro 2020 has now officially been postponed to 2021 by UEFA - but what happens now? What will the tournament look like? What happens to the Champions League and Europa League?