Disable password based authentication and only permit SSO with Office 365
Login page displays username and password forms
Steps to reproduce the behavior:
see login page
Resolved it myself. For anyone wondering, you can just delete the marked code after stopping zammad service, run sudo zammad run rake assets:precompile and start zammad again. It seems one would have to redo this after ervey zammad update since the file gets recreated. At least thats what I experienced.