To be a little more concrete, here's an example:

  <%= live_patch "about", to: Routes.about_path(@socket, :index) %>

which creates:

  <a href="/about" data-phx-link="patch" data-phx-link-state="push">about</a>

The data attributes are read by the LiveView HTML and are otherwise ignored by a JSless broswer.

Edited to fix glaring code sample error.

You can design singularly for LiveView and it handles everything. But if you want both request/response and LiveView (e.g. to mix the two or fallback to r/r when no js) you have to be more explicit in your design. It’s mostly trivial though. I have authentication pages that use the old controllers but pages that use only LiveView without any hassle.

Nope, all you need to do is make sure that everything has a route (which is very much encouraged in LiveView) and it works.