I built a Jekyll site locally (Jekyll version 4.1.1) and the theme I'm using is Hydeout 4.1.0. The site runs fine locally. I've pushed it to my repository on github and it says the site is published, but the page loads to just a white space.
You just need to change theme: jekyll-theme-hydeout
to remote_theme: fongandrew/hydeout
and it is working.
I am creating you a pull request on your repo incorporating this change.
Reference: https://stackoverflow.com/a/52103672/11474769 and usage section of this https://github.com/fongandrew/hydeout/