Very reminiscent of the Teleport access proxy which started out as a SSH proxy but now also supports a bunch of other protocols: https://github.com/gravitational/teleport
But SSO support does feel like an enterprise feature that people typically pay for.
I can’t think of any other feature gate that would work as well for software such as this. Though it typically is the largest hinderance to SSO adoption.
Obviously big companies will pay for SSO because they must have SSO. At my scale I skip products that are overpricing SSO or I put them behind a oauth2-proxy when I can.