Some ad detection code adapted from @simple-hacker

pbp-test.js

/// twitch-videoad.js
const origFetch = window.fetch;
window.fetch = (url, init, ...args) => {
	if (typeof url === "string") {
		if (url.includes("/access_token")) {
			url = url.replace("player_type=site", "player_type=thunderdome");
		} else if (
			url.includes("/gql") &&
			init &&
			typeof init.body === "string" &&
			init.body.includes("PlaybackAccessToken")
		) {
			const newBody = JSON.parse(init.body);
			newBody.variables.playerType = "thunderdome";
			init.body = JSON.stringify(newBody);
		}
	}
	return origFetch(url, init, ...args);
};
const attachMutationObserver = () => {
	const videoPlayer = document.querySelector(".video-player");
	if (!videoPlayer) return;
	const adObserver = new MutationObserver(() => {
		const ad = videoPlayer.querySelector(
			'[data-test-selector="ad-banner-default-text"]'
		);
		if (ad) {
			console.log("Ad detected, swapping to picture-by-picture player.");
			const mainVideo = document.querySelector(
				".video-player__container video"
			);
			const pbypContainer = document.querySelector(
				".picture-by-picture-player"
			);
			const pbypVideo = pbypContainer.querySelector("video");
			if (pbypVideo.muted) pbypVideo.volume = mainVideo.volume;
			pbypVideo.muted = mainVideo.muted;
			pbypVideo.style.width = `${mainVideo.offsetWidth}px`;
			pbypVideo.style.height = `${mainVideo.offsetHeight}px`;
			pbypContainer.style.opacity = "1";
			pbypContainer.style.pointerEvents = "none";
			pbypContainer.style.position = "absolute";
			pbypContainer.style.left = `-${mainVideo.offsetWidth}px`;
			pbypContainer.style.zIndex = "9999";
			pbypContainer.style.overflow = "visible";
			pbypContainer.querySelector(".tw-aspect").style.overflow = "visible";
		} else {
			const pbypContainer = document.querySelector(
				".picture-by-picture-player"
			);
			const pbypVideo = pbypContainer && pbypContainer.querySelector("video");
			if (pbypVideo) {
				pbypVideo.muted = true;
				pbypContainer.style.opacity = "0";
			}
		}
	});
	adObserver.observe(videoPlayer, {
		childList: true,
		subtree: true,
	});
};
window.onload = () => {
	attachMutationObserver();
	const pushState = history.pushState;
	history.pushState = (...args) => {
		pushState(...args);
		attachMutationObserver();
	};
};