What activities can a Product Owner undertake between the end of the current Sprint and the start of the next?

The most appropriate activity for a Product Owner between Sprints is to meet with stakeholders for feedback. This interaction provides valuable insights and ensures that the Product Owner is aligned with stakeholder expectations and market needs. Engaging with stakeholders helps to clarify any uncertainties, prioritize changes, and adjust the product backlog based on feedback received.

While it's crucial to maintain a continuous flow of work, particularly in the Scrum framework, the idea that the next Sprint starts immediately without any activities in between isn't practical. Sprint planning often benefits from the insights gained through stakeholder interaction, which allows the Product Owner to make informed decisions about the backlog and upcoming Sprint goals.

Conversely, reviewing past Sprints, planning for quarterly reviews, and other types of planning can be beneficial, but they must not take precedence over the direct engagement with stakeholders which can lead to a more informed product direction and enhances the collaboration aspect of Scrum. This responsive approach ensures that the team delivers higher value to both the customers and the organization overall.