YouTubeGridItemsFixer.js

// ==UserScript==
// @name         YouTube Grid Items Fixer
// @version      0.1
// @description  fix grid item count
// @author       Twister (https://github.com/twist84)
// @match        *://*.youtube.com/*
// @run-at       document-start
// @grant        none
// ==/UserScript==

let a1 = false;

function update_grid_css(milliseconds, column_count)
{
	const interval = setInterval(() =>
	{
		if (!a1)
		{
			document.querySelectorAll('ytd-rich-grid-renderer').forEach(grid_entry =>
			{
				document.querySelectorAll('ytd-rich-item-renderer').forEach(item_entry =>
				{
					if (item_entry.attributes.hasOwnProperty("is-in-first-column"))
					{
						item_entry.attributes.removeNamedItem("is-in-first-column");
					}
				});
				grid_entry.style.cssText = `--ytd-rich-grid-items-per-row: ${column_count}; --ytd-rich-grid-posts-per-row: ${column_count}; --ytd-rich-grid-slim-items-per-row: ${column_count}; --ytd-rich-grid-game-cards-per-row: ${column_count}; `;
			});
		}
	}, milliseconds);

	if (a1)
	{
		console.log(interval, a1);
		clearInterval(interval);
	}
	else
	{
		console.log(interval, a1);
	}

	return interval;
}

(function() {
	'use strict';

	let interval = update_grid_css(250, 5);
})();