/* Target both html and body to be safe, and use !important */
html, body {
    background: linear-gradient(-20deg, #2b5876 0%, #4e4376 100%) !important;
    background-attachment: fixed !important;
    background-repeat: no-repeat !important;
    background-size: cover !important;
}

/* Homepage often applies background colors to the main layout div.
   This makes that container transparent so your gradient shows through. */
#main-layout, .layout, #__next {
    background-color: transparent !important;
    background-image: none !important;
}