I see what’s happening! The issue is that your script is trying to modify styles using element.style, but that only works for inline styles—and most of the time, user-select: none is applied through CSS stylesheets, not inline styles. That’s why your changes aren’t sticking.

Why isn’t it working?

1. element.style.userSelect only affects inline styles. If user-select: none comes from an external CSS file, element.style.userSelect won’t see it at all.
2. Even element.style.cssText.replace(...) won’t help, because it doesn’t affect styles defined in a stylesheet.
3. DevTools (F12) shows "computed styles," not inline styles. You might see user-select: none in DevTools, but that doesn’t mean it’s an inline style.

How to Fix

Instead of modifying styles element-by-element, you should inject a new global CSS rule that overrides the existing one.

const style = document.createElement('style');
style.innerHTML = `* { user-select: contain !important; }`;
document.head.appendChild(style);