I think it's often better to "pick your poison" in terms of cloud providers and commit to it, with a rough migration plan that you can execute if you have to. There'll be common patterns in your systems that can be repeated if a large-scale lift-and-shift has to happen for some reason. But it's never easy, and I've found different clouds to have their own idiosyncrasies that make migration difficult - larger migrations will inevitably take time, effort, and lots of planning.
If you're looking for alternatives, or something lighter weight than Kubernetes, I've used Nomad (plus Terraform and Ansible) and some shell scripts to get repeatable clusters deployed and migrated between cloud providers: https://www.nomadproject.io/
If you're looking for alternatives, or something lighter weight than Kubernetes, I've used Nomad (plus Terraform and Ansible) and some shell scripts to get repeatable clusters deployed and migrated between cloud providers: https://www.nomadproject.io/