I also recommend Brendan's suggestion...
You could write some code to execute a scheduled task to call an API to get those posts and add them to your content.
I'm not sure what other kinds of options you are imaging might exist. You are asking for a way to...
- Programmatically make requests to arbitrary URLs/web pages on the internet
- Consume that HTML in some way
- Store that content in Xperience's headless items in a headless channel
- "Automatically" repeat this process on some interval you determine
There's no pre-built feature in Xperience by Kentico that lets you scrape the internet on a schedule and generate content items from that scrape.