Platform Engineering is 40% Technology, 40% People, Mindset, and Process, and 20% your company's individual demands.
I like to say, to become a platform engineer, you have to master different roles. Cloud Engineer, DevOps, Requirements Engineer, maybe even SRE, Security Specialist or Ops.
My recommendation:
• start with a cloud provider and IaC
• go down on containers and Kubernetes
• learn CI/CD and GitOps
• master security
• manage observability