Did you hear about SCIM, "System for Cross-domain Identity Management"? If combining with OIDC, then, seems to me one gets a more modern alternative to SAML. I've read just a bit about SCIM though.

SCIM: https://docs.microsoft.com/en-us/azure/active-directory/app-...

I wrote more in this comment: https://news.ycombinator.com/item?id=25425665

(What's your project about?)