I use the free Kadence theme for my website and in my view it is the best free WordPress theme for LearnDash courses since it provides so many useful features out-of-the-box.
It is pretty fast, and the free version includes a lot of useful features.
Replicate Focus Mode without losing the Navigation Bar
LearnDash focus mode provides a really nice user interface, but one of its downsides is that it removes the top level navigation bar.
You can see that I have replicated the look of the Focus Mode on my website, but you can still see the top-level navigation, which includes the search box.
Here is how I did it:
That is of course the purpose of the focus mode, but if you want to replicate the same look you can do that using the Kadence theme quite easily.
You do this by creating a custom sidebar specific to the LearnDash Lesson Post Type.
And in the Widgets, add the Course Navigation block into this custom sidebar.
The one downside of the Kadence theme is that it looks quite plain, but I personally find that it is not distracting and consider it a feature for online courses.