Getting public readable content indexed by google and other search engines

Looking for some advice. I need to get the public viewable content of the site to show up in google search results.

After searching here, as well as googling web, I found this page where the solution is to add the rss as sitemaps in google webmaster tools

I tried adding it but get a not found error(404), so I think I am not providing it a proper rss feed


I searched again and found this for an older elgg version

This which looks like it will work with modern versions

and even this, a 3rd party program

I am running 1.8.16

How does the community get their content indexed properly within a short time period?

Are any of the plugins here useful?

Why was this not functionality not built into elgg core(or am I missing something)?