Reverse Proxy - Admin console generates URL from public IP of client

I’ve got KC running behind Nginx, which is forwarding requests to a local backend where KC is installed.
Besides act8bg as a reverse proxy, Nginx also handles HTTPS and an SSL certificate issued by LetsEncrypt.

Accessing KC’s main screen poses no problem.

Nonetheless, when trying to access the admin console at /auth/admin/, the public IP of the client machine is used to build the URL, instead of the subdomain.
It should be, instead of

KC’s server log remains silent on this matter.

I have tweaked Nginx’s config file by following recommendations that KC users have posted and the proper headers seem to be sent to the backend.

Also checked the relevant potion of the installation guide.

Any help would be much appreciated.