Unreal Engine vs. Explicit HTTP Proxy -how to install?

Unreal Engine vs. Explicit HTTP Proxy

We tried to install the Unreal Engine in a network environment where no public DNS resolution and no public IP routing / access is available. The only way to request public URLs is an explicit HTTP proxy. Alternatively there is also a SOCKS proxy. We discovered the following behavior: As long as the installer application (epicsoftwareLauncher) is not able to resolve public DNS names, an error message is displayed and it is not possible to continue the installation process.

Is there any possibility to get the Unreal Engine installed in an environment like this? Can the Engine be configured to work with proxies (e.g. starting the installer with parameters) or is there even some kind of an offline installer?