I'm waiting for more real world production examples and not just the todo-list hello world.
I like the simpler/cleaner approach of Nue. Now one of the big difference will be the component and theming provided.
I'm a long term vue/vuetify user and i can build powerful and sexy web app in a small amount of time and effort.
I will definetely compare this point.
That's said, you've done an incredible work with your Nue project. i keep a eye on it.
What i mean is that classes are used to save interactive state and if you have some component like dropdown or hamburger menu then adding class "open" is very common solution and for certain transitions you need multiple classes because of in-out durations. So what you do? Use custom attributes? Sure but then thats just semantic difference to using a class attribute.
Looking at docs of your project you are doing both
posts.forEach(post => post.classList.add('fade-in'))
AND
main.style.display = 'block'
So whats with those claims?!