Is a multi-cloud strategy right for a startup?

It makes sense because Cloud is very expensive. You should try to Dev/Test/Qa in a cheap cloud. Usually they are very stable.

Then, with your CI/CD pipelines you should use a more stable and potentially more expensive cloud for PROD or a live environment. Your branch should be in always ready to deploy in the live environment.

If you already layer your startup to easily move from 1 cloud to another, then your startup should instantly benefit from the cheap cost to develop and stability for your clients. Also, at a later point you will be already ready to use multiclouds in the live environment.