I have created an easier, well documented version of this in my blog at https://blog.wyraz.de/linux/deploying-rancher-server-standalone-behind-traefik-with-lets-encrypt-for-both/
I have created an easier, well documented version of this in my blog at https://blog.wyraz.de/linux/deploying-rancher-server-standalone-behind-traefik-with-lets-encrypt-for-both/