In the course of a project, new stakeholders are often added, while others lose interest. Therefore, make it a habit - as always in agile development - to take a look at the stakeholder list at the beginning of a new iteration, for example.

As soon as you start developing a system, in addition to those interested in the system itself, all the people working on the technical realization (architects, development teams, infrastructure managers, delivery people, maintenance teams, hotline, trainers, …) will join.

They are all good sources for new requirements or hints that do not come from your end customers, users or buyers. Make use of their knowledge!