You can simplify the entry of the ICG server address for your users with a simple DNS tweak.

Add a TXT record for the host igel-cloud-gateway with the contents https://[ICG IP address]:8443/usg/endpoint
When users enter their email address user@example.com as the server address in the ICG Agent Setup, the setup will look up this record on the example.com nameserver and find the gateway address to connect to.