Bootstrap 4 Navbar and content fill height flexbox

Instead of using h-100 on the yellow content area, add an extra CSS class to make it flex-grow:1 in height...

.flex-fill {
  flex:1 1 auto;
}

https://www.codeply.com/go/xBAMfbHqbN

<div class="container-fluid h-100 d-flex flex-column">
    <nav class="navbar navbar-expand-sm s-navbar">
        <a class="brand navbar-brand" href="/">Brand</a>
        <button class="navbar-toggler s-btn-hamburger order-first s-color-icons" aria-expanded="true" aria-controls="navbar-test" aria-label="Toggle navigation" type="button" data-target="#navbar-test" data-toggle="collapse">
            <span class="navbar-toggler-icon k-icon k-icon-md k-i-hamburger"></span>
        </button>
        <div class="navbar-collapse s-menu-content collapse show" id="navbar-test">
            <ul class="navbar-nav mr-auto">
                <li class="nav-item dropdown">
                    <a class="nav-link dropdown-toggle" id="dropdown1" aria-expanded="false" aria-haspopup="true" data-toggle="dropdown">Menu Item</a>
                    <div class="dropdown-menu" aria-labelledby="dropdown1">
                        <a class="dropdown-item" href="/Device">Sub menu</a>
                    </div>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="/Test">Test</a>
                </li>
            </ul>
        </div>
    </nav>
    <div class="row flex-fill">
        <main class="col" style="background-color: yellow"></main>
    </div>
</div>

Note: The flex-fill utility class will be included in the next Bootstrap 4.1 release: https://github.com/twbs/bootstrap/commit/2137d61eacbd962ea41e16a492da8b1d1597d3d9

(Updated Bootstrap 4.1 demo)

Related question: Bootstrap 4: How to make the row stretch remaining height?