NextCloud Docker Cloudflare Tunnel trusted domains error

Hello, I put nextcloud on an Ubuntu server via Docker. I can reach this via the local IPv4 192.168.178.2. Now I would like to make this accessible from outside using Cloudflare Tunnels. The tunnel is already set up and functional. Only when I access the domain now do I get the error: Access via an untrustworthy domain. I can’t get the domain to be trusted. I’ve already tried a lot of things (adjusting environment variables, creating and configuring config.php). Can anyone help here?

Which Docker image?

Is the domain listed in your running configuration when you run occ config:list system?