Though we were not hit by the recent S3 outage, it definitely raised the question of putting all your eggs in one basket. I was thinking of at least starting with deploying your web server across these platform with A records pointing to them. Is there any such solution? Deployment could become provider agnostic? Just update your config files with IAM credentials and it'll deploy to all configured providers.
I never looked for a managed solution for this, but my approach if I had to prepare to manage this to reduce the locked-in would be:
There are real big challenges there, and we're only considering the payloads here, but you should also consider if your code directly uses S3 (which is common), or similar other app-level dependencies to AWS tech.
Finally another real challenge is to know and mitigate your third-party dependency to AWS if that's really what you need to achieve.
If the goal is resiliency rather than avoiding locked-in, I'd recommend considering multi-region HA rather than multi-cloud provider.
Siddarthan Sarumathi Pandian
Full Stack Dev at Agentdesks | Ex Hashnode | Ex Shippable | Ex Altair Engineering
If I understand your question correctly, you would like to deploy your services across platforms.
Shippable is a kickass CI/CD tool that'll help you do this. They have this product called Pipelines using which you can use to deploy your code at the same time to multiple cloud providers. All you need to do is to create the multiple integrations from their UI (IAM or AWS access key and ID for AWS, the project key for Google etc).
Let me know if you would need more help, I used to work at Shippable. Vishnu Bharathi works there and perhaps he can help you out with getting started.