here it is. i am however showing the preview image and replacing it with the iframe on click. basically click2load. by using mutationobserver it seems i don't need ublock to block the iframe, because as soon as the browser tries to include it on the page it gets replaced anyway

(function() {
'use strict';

const SITE = "https://www.youtube.com";
const LINK_TO_TIMESTAMP = true;
const SHOW_PREVIEW_IMAGE = true;

const createPreviewElement = (videoId, newURL, frame) => {
const container = document.createElement("div");
container.setAttribute('data-yt-preview', 'true');
container.style.position = "relative";
container.style.width = frame.width + "px";
container.style.height = frame.height + "px";
container.style.cursor = "pointer";

const img = document.createElement("img");
img.src = `https://i.ytimg.com/vi/${videoId}/mqdefault.jpg`;
img.alt = "Preview image of Youtube video";
img.style.width = "100%";
img.style.height = "100%";
img.style.objectFit = "cover";

const playButton = document.createElement("div");
playButton.innerHTML = "▶";
playButton.style.position = "absolute";
playButton.style.top = "50%";
playButton.style.left = "50%";
playButton.style.transform = "translate(-50%, -50%)";
playButton.style.fontSize = "48px";
playButton.style.color = "white";
playButton.style.backgroundColor = "rgba(0, 0, 0, 0.7)";
playButton.style.borderRadius = "50%";
playButton.style.width = "80px";
playButton.style.height = "80px";
playButton.style.display = "flex";
playButton.style.justifyContent = "center";
playButton.style.alignItems = "center";

container.appendChild(img);
container.appendChild(playButton);

container.addEventListener("click", () => {
const iframe = document.createElement("iframe");
iframe.src = frame.src + (frame.src.includes('?') ? '&' : '?') + 'autoplay=1';
iframe.width = frame.width;
iframe.height = frame.height;
iframe.frameBorder = "0";
iframe.allow = "accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture";
iframe.allowFullscreen = true;
iframe.setAttribute('data-yt-processed', 'true');
container.parentNode.replaceChild(iframe, container);
});

return container;
};

const replaceEmbed = (frame) => {
const frameURL = frame.src || frame.dataset?.src;
if (!frameURL) return;
const match = frameURL.match(/(^https?:)?\/\/(www\.)?youtube(-nocookie)?\.com\/embed\/([a-zA-Z0-9\-_]{11}).*?(\?.*((t|start)=([\dsmh]*)))?/i);
if (match?.length == 9) {
const videoId = match[4];
const newURL = SITE + "/watch?" + ((LINK_TO_TIMESTAMP && match[8]) ? "t=" + match[8] + "&" : "") + "v=" + videoId;

const previewElement = createPreviewElement(videoId, newURL, frame);
frame.parentNode.replaceChild(previewElement, frame);

// common lazyload hiding methods
previewElement.style.display = "block !important";
previewElement.style.opacity = "100% !important";
previewElement.style.background = "transparent !important";
const parent = previewElement.parentElement;
if (parent) {
parent.style.display = "block !important";
parent.style.opacity = "100% !important";
parent.style.background = "transparent !important";
}
}
};

const observeDOM = () => {
const observer = new MutationObserver((mutations) => {
mutations.forEach((mutation) => {
if (mutation.type === 'childList') {
mutation.addedNodes.forEach((node) => {
if (node.nodeType === Node.ELEMENT_NODE) {
if (node.tagName === 'IFRAME' && !node.hasAttribute('data-yt-processed')) {
replaceEmbed(node);
} else {
node.querySelectorAll('iframe:not([data-yt-processed])').forEach(replaceEmbed);
}
}
});
}
});
});

observer.observe(document.body, {
childList: true,
subtree: true
});
};

// Initial replacement
document.querySelectorAll('iframe:not([data-yt-processed])').forEach(replaceEmbed);

// Start observing DOM changes
observeDOM();

})();