As a sanity check, I just completed the same setup that you described (Ubuntu Server 24.04 running in a Proxmox VM, Domain name pointing to a CNAME that points to the Dynamic IP, using the installer script, enabled CrowdSec, etc.), and everything worked out of the box. A couple of things I noticed that would also be worth checking now that I’m more familiar with this specific setup are:

• In the config/config.yml file, verify that the dashboard_url is set to the FQDN of the full URL (e.g. pangolin.mydomain.com), and that the base_domain is set to the root/apex domain (e.g. mydomain.com).
• Double check those DNS records. As the haiku goes: it’s not DNS, it couldn’t be DNS, it was DNS. dig pangolin.mydomain.com or dig @1.1.1.1 pangolin.mydomain.com should show the CNAME that points to the A record.
• A 404 page not found error is normal when connecting to the IP address directly rather than using the domain name. I was successfully able to access the dashboard using the FQDN from a local and external network. Depending on your network, you might want to set up a local DNS record that points to the internal IP address as well (though this should be optional in most cases to my knowledge).

I hope that helps!