Which Stakeholder works with the Agile BA to prepare the users of the solution working...

The Business Ambassador works with the Agile BA to prepare the users of the solution within the relevant business area for each incremental deployment of an evolving solution. The Business Ambassador acts as a liaison between the development team and the end users, ensuring that the requirements and feedback are effectively communicated and that the users are ready to adopt the new increments of the solution as they are deployed.

References:

Business Analysis.pdf, "The role of the business analyst in an Agile environment...supporting the business users"​​.