Allegedly, on or about 27 March 2018, Peter Bittner sent:
The IPA Server hostname must not resolve to localhost(127.0.0.1). A routable IP address must be used. [...]
Is there any way to make a local install happen? Or what do I have to do instead?
It wants an IP that can be reached by other equipment. It may be sufficient to use an address that other equipment on your LAN can access (like the 192.168.0.0 range of IPs), or you may need a public IP address.
And if you have a routable IP, your computer's hostname should point to it, too, not the local loopback IP. So if your /etc/hosts file looks like this:
127.0.0.1 localhost localhost.localdomain hostname hostname.localdomain
Move the non-local addresses out of the 127.0.0.1 information line, more like this kind of thing:
127.0.0.1 localhost localhost.localdomain 192.168.0.1 mycomputer mycomputer.example.com