There's always keycloak you can rollout yourself. It's not trivial but it's quite doable.
edit: looks like there are affordable managed hosting providers for keycloak.
Not sure the state of keycloak now, but it was a lot of work to manage keycloak configs with the IaC pipeline. That could have gotten better now, but I think having access to the data is important because migration might not be trivial if for instance a provider starts acting up.