GitHub Pages build cannot find bootstrap sass

I have a GitHub pages site (a project page) that uses Jekyll and would like to use Bootstrap in my project.
I downloaded the uncompiled twbs files and added the bootstrap, mixins and utilities folders under a _sass directory in my project.

I import bootstrap in my main sass file like so:

@import 'bootstrap/bootstrap';

This works fine locally when I run bundle exec jekyll serve.

However when I push the build to GitHub Pages I get the following error:

Your SCSS file ci-dashboard/assets/css/style.scss has an error on line 2: File to import not found or unreadable: bootstrap/bootstrap. Load path: /hoosegow/.bundle/ruby/2.7.0/gems/jekyll-theme-primer-0.5.4/_sass.

I have tried the following:

  1. Adding this to my _config.yml file
    sass_dir: _sass
    style: compressed
  1. Following the instuctions in this post by adding a baseurl to my config.yml file and attempting to import bootstrap in my main css file with the following line:
@import '{{ site.baseurl }}/bootstrap/bootstrap';

This solution seemed very promising as it seems there’s an issue with jekyll and GitHub pages using relative links? I’m guessing I have that import wrong or in the wrong place?

  1. Replacing vendor in my .gitignore file with vendor/bundle as suggested by this post.

Here is the structure of my project:

├── _config.yml
├── _sass
│   ├── bootsrap
│   |   └──*lots of .scss files*
│   ├── mixins
│   |   └──*lots of .scss files*
│   └── utilities
│       └──*lots of .scss files*
├── assets
│   └── css
│       └──style.scss
├── _includes
│   ├── footer.html
│   └── header.html
├── _layouts
│   └── default.html
├── _site
└── Gemfile
etc. etc.