YT-DLP has a list of extractors for lots of different sites. You could see if there are similar sites and see how their extractors work.

https://github.com/yt-dlp/yt-dlp/tree/master/yt_dlp/extractor

Or Animescraper has extractors for them, but it was last updated 6 years ago.

https://github.com/jQwotos/animeDownloaders/tree/master

https://github.com/jQwotos/anime_scrapers/tree/63b415fcaaa685f03b54fe6ee294c13178736637/scrapers

Here is Anna’s Archives blog about how they are set up.

https://annas-blog.org/how-to-run-a-shadow-library.html