I have configured a user schema with:

"anyOf": [
                {
                    "required": ["email"]
                },
                {
                    "required": ["phone"]
                }
            ],

and it seems to work the way I would expect. (Other elements of getting the UI right for this are more challenging. But that’s a different story.) I didn’t see a github repo for the documentation site when I searched, but I thought this could be a good thing to add to an example on https://www.ory.sh/docs/kratos/manage-identities/customize-identity-schema