How to automate the interactive part of Digital Ocean one-click install?

I’m currently terraforming (via Terraform Cloud) a deploy to a Digital Ocean droplet, behind Cloudflare. As I’m planning to deploy a few such blogs, possibly in different environments (dev/prod), I’m quite keen on avoiding the SSH interactive part of the setup involved in the one-click Digital Ocean marketplace install.

I’m currently deploying the ghost-20-04 image on Digital Ocean. How can I best automate the last bit ? I couldn’t see any trace of which script runs upon first login as root on the box. I’d be quite keen to find it and adapt it for silent setup…

Thank you!