A few ansible scripts? Nah.
Everything I have runs in kubernetes. The only difficulty I have to deal with is figuring out how to deploy a kubernetes cluster in each provider.
From there, I write a single piece of orchestration that will drop my app stack in any cloud provider. I'm using a custom piece of software and event-driving automation to handle the creation and migration of services.
Migrating data across providers is hard as kubernetes doesn't have snapshots yet.
There are already a lot of startups in this space doing exactly the kind of thing that I just described. Most aim to provide a CD platform for k8s.
I just heard a dozen founders sit up and think "Market Opportunity" in glowing letters.
CockroachDB has a strong offering.
But multi-cloud need not be complicated in implementation.
A few ansible scripts and some fancy footwork with static filesystem synchronization and you too can be moving services from place to place with a clear chain of data custody.