Here is an idea that rely on background coloration and not mix-blend-mode. The trick is to have a gradient with the same dimension as the image that you move the same way to simulate the blend mode:
const box = document.querySelector(".box");
const h1 = document.querySelector("h1");
window.addEventListener('mousemove', function(event) {
box.style.left = `${event.pageX - 50}px`;
box.style.top = `${event.pageY - 50}px`;
h1.style.backgroundPosition = `${event.pageX - 50}px ${event.pageY - 50}px`;
});.wrapper {
background-color: white;
}
h1 {
position: relative;
z-index: 2;
color: white;
background:
/*gradient position / size */
linear-gradient(#fff,#fff) -100px -100px/100px 100px fixed no-repeat,
#000;
-webkit-background-clip: text;
background-clip: text;
-webkit-text-fill-color: transparent;
color: transparent;
}
.box {
width: 100px;
height: 100px;
position: absolute;
z-index: 1;
background-image: url("https://placekitten.com/100/100")
}<div class="wrapper">
<h1>Lorem Ipsum</h1>
</div>
<div class="box"></div>I have considered background-attachment:fixed to place the gradient relatively to the viewport since your element is position:absolute with no ancestor positioned so it’s also positioned relatively to the viewport.