All clouds provide jwks_uri endpoint for public key lookup, when using RSA256. It's possible to use RSA256 in Sphinx, but I do not see how to add a new endpoint with the key details (like the https://XXXXXX.oktapreview.com/oauth2/v1/keys URL), plus add that URL to the /.well-known/openid-configuration endpoints list.
Can it be done as it is now? Or would it need to be baked into the core components? - and if the latter, can you create an enhancement request for that, please?