What does this all mean from IaC perspective?

Let’s say you can define all your containers, orchestration, database and middleware in a compact way (Dockerfiles, Terraform, etc) with cloud vendor independent open source tools, using managed OSS.

How much of that code would be dependent on your cloud provider, really? Maybe a thousand lines of hopefully modularized platform dependent configuration code?

Migration from one system to another would still be an effort, but not that big one?