Like what Michael said, there are a number of companies willing to act as an adapter for your SSO needs. My employer, FusionAuth, is another.

Agreed that every SP is slightly different. There's a reason the SAML spec is 800+ pages, it covers a lot of variations. Since it has not been substantially updated since, there are some legacy choices (hello XML).

We also maintain an open source java SAML library: https://github.com/FusionAuth/fusionauth-samlv2

SSO is simple on the surface and complex once you peel it back!

Small plug for my startup (hope that's ok!!)

This is what WorkOS helps solve for developers. It's like Stripe for SAML (and other enterprise features)

https://workos.com/single-sign-on

Happy to chat with anyone who's interested! mg@workos.com