Ring certainly does work with Facebook Portal. The Facebook Portal has Alexa built-in, which means you just need to download the Amazon Alexa app and add the Ring Skill. I’d make sure your device(s) show up under the Alexa app.
Once that is done, ensure your Ring devices are showing on the Alexa app and that Alexa is running on your Facebook Portal, and then you can say “Alexa, show me my front door” for instance, to see video. 