The Sign in UI is displayed as a full page portlet on DXP (private bundles). This UI is different from the modal sign in seen in CE and legacy versions of portal.
Tomcat 9.0.33 + HSQL
Portal DXP master Git ID f0367b567ad4588375253a758a84f64c3d313829
Execute Manual Testing
Unable to login using CAS or SAML SP
Deploying SAML hook module disables login dialog