How to hide restricted nginx subdomains?

Question

To hide a restricted location, e.g.

location /secret/ {
 allow 10.0.0.0/24;
 deny all;
}

one could set

error_page 403 =404 /404.html;
error_page 404 /404.html;

to make impossible to distinguish a non-existing location (404) from a restricted one (403).

Is there a way to perform a similar spoof for subdomains?

I want https://admin.example.org/ to not NOT return 403 if not visited via VPN, but rather show the same of https://nonexistingsubdomain.example.org/ (e.g. a 301 redirect to https://example.org/)