How transferable are cloud skills when switching providers for a new job?

A lot carries over. Kubernetes concepts, Helm, Terraform and the general idea of how infrastructure fits together don't disappear when you change providers. Going from EKS to GKE shouldn't mean starting from scratch.

But the services aren't exact substitutes. IAM is a big one: AWS policies, GCP's resource hierarchy and Azure RBAC have different models. Networking, load balancers and managed data services can also take real time to learn.

I'd apply anyway, but be clear about which provider you've actually used. Strong EKS and Terraform experience is relevant to a GKE role. Saying you have GKE experience when you don't is a different thing.

Ask what the team uses day to day, too. A job description that mentions several clouds doesn't necessarily tell you which one you'll be working in most.

For prep, pick one service you already understand and trace how its equivalent is set up in the new cloud. Look at permissions, networking and resource dependencies, not just the service names. Terraform knowledge transfers, but the provider resources and modules still need learning.

Certification study material can be useful for getting familiar with the terminology and core services, even if you don't plan to take the exam.

Kubernetes can give you a common way to run workloads across providers, which makes switching less daunting. It doesn't make the whole infrastructure portable, though. The cloud resources supporting a cluster still have their own configuration and quirks.