Usually depending on the state of our initiative:
#1 start of the platform: here I work a lot with EA, because I need list of all systems, business capabilities, technologies being used and teams - to decide on platform tech stack, to select migration strategy for systems and to identify teams I need to analyze (I do value stream mapping and maturity assessment, the whole analysis framework I’ve put in my course:
https://drogaarchitektait.pl/en/efficient-platform-manager-global/, how I approach it is here:
https://khalasa.com/2024/01/how-to-approach-internal-developer-platform-delivery/ )
#2: if we are already platforming for some time: EA helps me to plan future services of the Platform, because they are first to know that there will be new delivery / SaaS / product purchase initiative, which will be supported by the platform. Scope is similar to #1, but usually smaller