In general this is a decent article on non-JavaScript-based mobile navigation options, but what I found most interesting is the idea of having a separate page for your navigation menu (at the URL /menu, for example).
Who said navigation has to be in the header of every page? If your front end is extremely lightweight or if you have a long list of menu items to display in your navigation, the most practical method might be to create a separate page to list them all.
I also noted that the article describes a method where you can “spoof” a slide-in hamburger menu without JS by using the checkbox hack. I once coded a similar “HTML and CSS -only” hamburger menu, but opted instead to use the :target pseudo-class in combination with the adjacent sibling selector, as described by Chris Coyier back in 2012.