That sounds like an awful experience! Can you clarify, are you hoping to have a landing page presented to users, where they would need to click to authenticate to Tableau Server using your SAML provider? Or are you hoping to avoid having a landing page for users?
When Tableau Server is set up for SAML, users who access your Tableau Server url will be automatically redirected to your SAML IdP without a landing page. This seamless sign in experience is one of the reasons many people choose to use SAML authentication.
If you'd like to have a landing page, you could create and host a web page for your users to access, with a button that would take them on to Tableau Server - but it would need to be a page created and hosted outside of Tableau Server.
I hope this helps! Please let me know if I did not understand your question, and I'll try again