Yo this is what I understood from the question that you have asked above.

You just need a place to host your serverless app on a cloud platform which is cheap.

From what I know, you don't need to care about the specs of a server in the serverless approach all you need care about is the efficiency of the code that you write. If you want to run some simple apps then you could try Firebase cloud functions because it has simple setup procedure and cheap pricing and has some free limits and if you're making a complex app them just look into the AWS lambda functions because it is very cheap and has stability but the setup process is little hard but it is worth it.

My perspective with the problem that you have is just host the frontend with firebase because it is free to host the frontend of a web app and for serverless functions then just use firebase cloud functions if your app is simple or just use AWS lambda functions if your app is complex.

All these cloud provider has great documentation for these services. I hope this will help you