Digital transformations all over the world intend to create or influence socio-technical ecosystems in which people and organizations are collaborating today. Many of these digitization efforts are characterized as partial or total failures, as they could not master the high complexity of a focal ecosystem, including a large number of involved actors, multi-branched collaboration processes and heterogeneous IT landscapes. In an intra-organizational context, enterprise architecture (EA) models are used to receive transparency on relations and to handle the complexity of digital transformations. This paper aims to extend the idea of EA modeling to the ecosystem level to support project managers in performing digital transformations of ultra-large scale. By conducting four case studies on digitization projects in different industries, we identified six architectural perspectives with forty stakeholder concerns on ultra-large scale digital transformations. For addressing these concerns, an ecosystem architecture meta-model is developed and demonstrated.