Feels like you might be overthinking this. Most of the tools you listed already cover 90% of what you’re asking for. If you’re starting a SaaS from scratch and haven’t got a single user yet, sinking too much time into picking the “perfect” auth solution will slow you down more than making a “wrong” choice ever will. The bigger risk is not shipping at all.

I’ve worked with Supabase, Clerk, Keycloak, and Kratos on different projects. None of the open-source options truly deliver on “low management overhead”. You’ll always have to deal with updates, patches, and some manual babysitting.

If you refuse to compromise on your feature list, your realistic options shrink fast. In that case, Zitadel is a solid choice, but be ready for higher costs from day one. My advice is to trim the must-have list, go with a managed service, get real users, and revisit the decision when scale actually becomes a problem.