Greasy Fork

Fixed:

// ==UserScript==
// @name Plex auto-skip intro
// @namespace https://greasyfork.org/en/users/555204-bcldvd
// @version 0.1
// @icon https://www.google.com/s2/favicons?domain=plex.tv
// @description Automatically press the Plex "Skip intro" button when it appears.
// @author David Boclé
// @match https://app.plex.tv/desktop/
// @grant none
// ==/UserScript==

(function() {
let element = document.getElementById('plex');
let observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
if(mutation.addedNodes.length > 0 && mutation.addedNodes[0] && mutation.addedNodes[0].innerText == 'SKIP INTRO') {
setTimeout(() => {
mutation.addedNodes[0].firstChild.click()
}, 10);
}
});
});
observer.observe(element, { childList: true, subtree: true });
})();

I'll keep an updated version going here: https://greasyfork.org/en/scripts/441696-fixed-plex-auto-skip-intro