I'm doing this in docker since macOS' Ruby is weird and broken.
Grab the image:
docker pull machines/jekyll
Update the gemfile:
docker run --rm \
--mount type=bind,source="$PWD",target=/srv/jekyll \
--publish 4000:4000 \
jekyll/jekyll \
bundle update
Run it in "serve" mode:
docker run --rm \
--mount type=bind,source="$PWD",target=/srv/jekyll \
--publish 4000:4000 \
jekyll/jekyll \
jekyll serve
This'll expose it on http://localhost:4000, open the link and you should see the site.