My goal is to avoid manual configuration of the license server:
Help > Register > IntelliJ IDEA License Activation Dialog is opened > License server
I asked the same question on the IntelliJ IDEA Help Center and got an answer from JetBrains support employee: https://intellij-support.jetbrains.com/hc/en-us/community/posts/206666999
Seems that there is no IntelliJ configuration property to setup the license server.
The options are either to configure the DNS lookup or to copy an existing key into the config folder.