Need help figuring out post previews as excerpts and setup

I am trying to setup my blog such that when I post links on other websites, it will embed with a preview of the first paragraph of the post.

I looked at the jekyll docs which recommended

By default this is the first paragraph of content in the post, however it can be customized by setting a excerpt_separator variable in front matter or _config.yml .
One of my friends noticed that my head.html had differed from their config

  <meta name="description" content="{{ page.excerpt | default: site.description | strip_html | normalize_whitespace | truncate: 160 | escape }}">

My head.html file generated when cloning the original repository

<meta name="viewport" content="width=device-width, initial-scale=1">

I have tried

   <meta name="{{ page.excerpt | default: site.description }}">

which maintains formatting, but the embedding is still the same

Am I looking at the wrong file? What do I need to change to make it work?