How to get all topics from a specific category using offset/page param in the API query?

You can use this - https://docs.discourse.org/#tag/Search/operation/search (scroll down!)

You’ll see that besides ?q, we also have ?page, so..

https://{default_host}/search.json?q=%23courses%3Amlt-kb%20after%3A2024-09-24%20before%3A2024-12-29&page=1