Alexa Smart Home Integration - using Traefik with Google OAuth

I am running Home Assistant in a docker container (Ubuntu 20.04) and am making use of Traefik + Google OAuth for each of my containers, including HA, running in the environment.

I am attempting to configure the Smart Home Skill according to https://www.home-assistant.io/integrations/alexa.smart_home/, but an running into trouble when trying to use Google OAuth as the authentication mechanism.

No matter which way I try, Alexa tells me to see this guide for instructions on configuring skill for account linking with OAuth.

Can anyone help?