Full disclosure I work at a company attempting to address this very problem. - https://www.facets.cloud/multi-cloud-infrastructure So, what we do is, create cloud-agnonstic YAML files that can be plugged into any cloud. So an AWS RDS effortlessly transforms into a CloudSQL in GCP and a flexible server in Azure.

And this is possible because we follow an architecture-first approach. We have blueprints where you define your architecture, and plug that template to any cloud provider.