Create Fake FE in TYPO3 Backend for proper FE link generation from BE

gistfile1.php

<?php
class Foo {
	protected function buildFakeFE($pageUid) {
		// clear session key to avoid FE cookies
		$oldGETSessionKey = '';
		if (isset($GLOBALS['_GET']['FE_SESSION_KEY'])) {
			$oldGETSessionKey = $GLOBALS['_GET']['FE_SESSION_KEY'];
		}
		$oldPOSTSessionKey = '';
		if (isset($GLOBALS['_POST']['FE_SESSION_KEY'])) {
			$oldPOSTSessionKey = $GLOBALS['_POST']['FE_SESSION_KEY'];
		}
		$GLOBALS['_POST']['FE_SESSION_KEY'] = '';
		$GLOBALS['_GET']['FE_SESSION_KEY'] = '';

		// simulate FE session to get TypoScript config from given PID
		$GLOBALS['TT'] = GeneralUtility::makeInstance(NullTimeTracker::class);

		// simulate a normal FE without any logged-in FE or BE user
		/** @var $fe TypoScriptFrontendController */
		$this->tsfe = GeneralUtility::makeInstance(TypoScriptFrontendController::class, $GLOBALS['TYPO3_CONF_VARS'], $pageUid, 0, 0, TRUE);
		$GLOBALS['TSFE'] = $this->tsfe;
		$this->tsfe->TYPO3_CONF_VARS['FE']['pageNotFound_handling'] = '';
		$this->tsfe->beUserLogin = FALSE;
		try {
			$this->tsfe->initFEuser();
			$this->tsfe->clear_preview();
			$this->tsfe->determineId();
			$this->tsfe->makeCacheHash();
			$this->tsfe->initTemplate();
			$this->tsfe->getFromCache();
			$this->tsfe->getConfigArray();
		} catch (\Exception $e) {
			return FALSE;
		}

		// calculate the absolute path prefix
		if (!empty($this->tsfe->config['config']['absRefPrefix'])) {
			$absRefPrefix = trim($this->tsfe->config['config']['absRefPrefix']);
			if ($absRefPrefix === 'auto') {
				$this->tsfe->absRefPrefix = GeneralUtility::getIndpEnv('TYPO3_SITE_PATH');
			} else {
				$this->tsfe->absRefPrefix = $absRefPrefix;
			}
		} else {
			$this->tsfe->absRefPrefix = '';
		}
		$this->tsfe->newCObj();

		// restore
		$GLOBALS['_GET']['FE_SESSION_KEY'] = $oldGETSessionKey;
		$GLOBALS['_POST']['FE_SESSION_KEY'] = $oldPOSTSessionKey;

		return TRUE;
	}
}