Custom domain
If you'd rather expose the server yourself, point your own domain at it. In Settings → Remote, set the direct connection method to Custom domain and enter the URL where the server is reachable, for example https://nvr.example.com.
This assumes you've already made the server reachable at that address, through your own DNS and a reverse proxy or port-forwarding on your router. camera.ui doesn't change your network for you here; it records the public address to use.
Use Test connection to confirm it works.
TIP
If you don't run your own domain or reverse proxy, camera.ui Cloud or a Cloudflare tunnel is simpler, since neither needs router changes.