<nav>
  <a href="#beginning">
   beginning
  </a>
  <a href="#middle">
   middle
  </a>
  <a href="#end">
   end
  </a>
</nav>

a:not(:hover) {
  text-decoration: none;
}

nav a {
  /* Has no effect */
  text-decoration: underline;
}

/* With the new :where Level 4 selector */
a:where(:not(:hover)) {
  text-decoration: none;
}

nav a {
  /* Should work */
  text-decoration: underline;
}