I recently made a fresh install and session.inc created continuous timeouts with redirects to the login page (ubuntu 20.04, PHP 7.4 as well as PHP8.0, FA 2.4.11). I was looking for hours at sessions with webservers and cookies but finally notrinos found the real culprit. Thanks.
WORKS:
$Session_manager->sessionStart('FA'.md5(dirname(__FILE__)));
CONTINUOUSLY TIMEOUTS SESSIONS:
$Session_manager->sessionStart('FA'.md5(dirname(__FILE__)), 0, '/', null, True);