If you clone the repo locally you also need to get the submodule files with git submodule update --init --recursive
You can use any local server to serve the files. One option is live-server (install it with npm install -g live-server then type live-server in the command line). Using a local server gives you additional features such as live-reload and some of the more advanced Reveal.js features.
Push completed slides back to GitHub
Configure your GitHub pages settings to serve the slides from youraccount.github.io/repositoryname (or custom domain even)
Amaze your friends by being able to share the URL of your live, interactive slides with your audience immediately. No more emailing PowerPoint attachments for YOU!
You may get Dependabot alerts from GitHub to warn you of vulnerabilities in the Reveal.js code. To make these go away, update the submodule.
To update you can use the script s/update which updates Reveal.js to latest. The first time you run this command (on some systems) you will need to make it executable, by running chmod +x s/update. This can also be done in the File Manager UI in many systems.
For older repositories made from this template, the command to run is git submodule update --rebase --remote, from the root of the repository (not the reveal.js submodule directory itself) to update.
link for info on updating submodules https://stackoverflow.com/questions/1979167/git-submodule-update