Add portal.adp.com for SSO
Thanks for your app request. In order to evaluate your request, can you please fill out this app request form at http://aka.ms/aadappsurvey? It will help us prioritize the request and be able to follow up with you.
Steve Whitcher commented
I filled out this survey last year, but have never heard anymore about it. Has there been any progress? Based on a previously closed request for supporting this same site, it seems that there is demand for it. . . (https://feedback.azure.com/forums/169401-azure-active-directory/suggestions/7079530-add-sso-app-for-adp-portal)