A custom template for Gitea to embed pages into tabs with an iframe. Requires the proper X-Frame-Options and Content-Security-Policy on the linked resource. The example below is how I use it for Drone. Install into data/gitea/templates/custom/extra_tabs.tmpl as described on https://docs.gitea.io/en-us/customizing-gitea/#customizing-gitea-pages

extra_tabs.tmpl

<a class="item" href="https://your.domain.here{{.RepoLink}}" data-iframe-tab="builds" title="Builds">
	<i class="octicon octicon-gear"></i> <img src="https://your.domain.here/api/badges{{.RepoLink}}/status.svg?ref=refs/heads/master" style="width: auto">
</a>

<script>
document.addEventListener('DOMContentLoaded', () => {
	const openFrame = (tab) => {
		const name = tab.dataset.iframeTab;
		const page = tab.href;

		const realTabsDivider = document.querySelector('.repository .ui.tabs.divider');
		realTabsDivider.style.marginBottom = '0';

		const realTabs = document.querySelector('.repository .ui.tabs.container > .navbar');
		for (let realTab of realTabs.children) {
			realTab.classList.remove('active');
		}
		tab.classList.add('active');

		let subtractHeight = realTabs.getBoundingClientRect().bottom;

		const iframe = document.createElement('iframe');
		iframe.src = page;
		iframe.frameBorder = 0;
		iframe.width = '100%';
		iframe.height = '560';
		iframe.style.height = 'calc(100vh - ' + subtractHeight + 'px)';

		const container = document.querySelector('.repository > .ui.container');
		container.style.width = '100%';
		container.style.marginLeft = '0';
		container.style.marginRight = '0';

		container.innerHTML = '';
		container.appendChild(iframe);

		document.body.style.overflow = 'hidden';

		window.location.assign('{{.RepoLink}}#' + name);

		window.addEventListener('resize', () => {
			subtractHeight = realTabs.getBoundingClientRect().bottom;
			iframe.style.height = 'calc(100vh - ' + subtractHeight + 'px)';
		});
	};

	const tabs = document.querySelectorAll('[data-iframe-tab]');
	for (let tab of tabs) {
		tab.addEventListener('click', e => {
			e.preventDefault();
			openFrame(tab);
		});
	}

	const hash = window.location.hash.replace('#', '');
	for (let tab of tabs) {
		if (tab.dataset.iframeTab == hash) {
			openFrame(tab);
			break;
		}
	}
});
</script>