how to use app platform for a basic html web app

I am trying to use App Platform to publish my basic web app. The web app is simply made of an html landing page, and a bunch of php files to access my MySQL database. I am migrating this all from Siteground, so theoretically the database credentials won’t work. I currently have a 5GB volume, 25GB Disk Ubuntu droplet, and a managed database.

This should all work with the App Platform. Here’s the problem, though: When I have it all set up, with the directory pointed at the folder /animalia inside my Github where my app main page and all relevant files are, it says “no component detected.” When i point it specifically to the /animalia/main.html file inside this folder, it says “detecting app.”

In any case though, it won’t let me go forward past the first page of selecting my Github repo. Therefore, I am wondering what is wrong, since the errors don’t make any sense. I am attaching my Github github.com/yav-fi/animalia/ for your reference.

Please let me know as soon as you can how I can get my HTML-based application up and running DigitalOcean, even if I don’t have to use App platform. Thank you!