Is it possible to fade-out the end of a text line in CSS?

Is something like this what you're looking for?

div {
  background: linear-gradient(to bottom right, red, yellow);
}
h2 {
    background-image: linear-gradient(90deg,#000000 0%,rgba(0,0,0,0));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    position:relative;
    display:inline-block;
    font-size: 50px;
}

<div>
  <h2>
    test test test test test
  </h2>
</div>

There is a sleek solution which uses mask-image. Yes, it uses a linear-gradient(), however, because it works with pure transparencies, no knowledge of the background color is necessary:

div {
  white-space: nowrap;
  -webkit-mask-image: linear-gradient(to right, rgba(0,0,0,1) 90%, rgba(0,0,0,0));
}

Works for me in Chrome and caniuse for mask-image looks not bad.