https://github.com/nextcloud/user_saml/issues/208
Edit this file:
/var/www/html/nextcloud/apps/user_saml/lib/Controller/SAMLController.php
search for @NoSameSiteCookieRequired and edit this line:
/**
* @PublicPage
* @NoCSRFRequired
* @UseSession
* // @OnlyUnauthenticatedUsers
* @NoSameSiteCookieRequired
*
* @return Http\RedirectResponse|void
*/
public function assertionConsumerService() {
$AuthNRequestID = $this->session->get('user_saml.AuthNRequestID');
// if(is_null($AuthNRequestID) || $AuthNRequestID === '') {
// return;
// }