The first thing that should be done to reduce the complexity of the IT landscape is to conduct strategic planning with business units. Strategic planning is the process of defining the vision, mission, goals, and objectives of the enterprise and how they will be achieved. It also involves aligning the IT strategy with the business strategy and ensuring that they support each other. By conducting strategic planning with business units, the enterprise can identify and prioritize the IT needs and expectations of each business unit, as well as the commonalities and synergies among them. This can help to reduce the complexity of the IT landscape by eliminating duplicate technologies, resolving conflicting priorities, and creating a coherent and consistent IT architecture that meets the business requirements and delivers value. The other options are not as effective as conducting strategic planning with business units for reducing the complexity of the IT landscape. Promoting automation tools used by the business units may improve efficiency and productivity, but it does not address the underlying issues of duplication and conflict. Migrating all in-house systems to an external cloud environment may reduce costs and increase scalability, but it does not ensure alignment and integration of IT systems across business units. Standardizing technology architecture on common products may simplify IT operations and maintenance, but it does not consider the specific needs and preferences of each business unit.