https://docs.pantheon.io/guides/sso/shibboleth-sso page says about drupal 10 sso.
Drupal 10 includes Symfony 6. The SimpleSAMLphp library is not currently compatible with Symfony 6 unless you use the dev-master branch. There is a new simplesamlphp_auth branch (4.x) that you can use if you require a compatibility workaround. Note that this workaround requires you to use dev versions at your own risk.
Can we consider using samlauth module instead.