Can I integrate with S3 bucket or digitalocean spaces?

It depends a bit on what you mean by integrate. You can’t upload to them via the file manager ‘out of the box’, but check out Treasury if that’s what you’re looking for.

No, you can’t do that. You can use digitalOcean block storage instead of integrating S3 bucket with digitalOcean spaces. You see, S3 works better with AWS but not DigitalOcean web server. I hope the point is cleared to you.