The best way to get NicInfo is as a Ruby gem. To do so, issue the following command:

gem install nicinfo

The gem install might take a few seconds building documentation, but don't worry. If that waiting is just unbearable, use this command to install without the documentation:

gem install nicinfo --no-ri --no-rdoc

Once it is installed, try nicinfo -h

NicInfo ships with a set of RDAP bootstrap files from the IANA. However, these files are always changing, and you may wish to update them from time to time: nicinfo --iana -V

Follow the instructions here

MacOS comes with a version Ruby that is bound to a very old version of OpenSSL, and that old version of OpenSSL will prevent connecting to RDAP servers using TLS 1.2 or higher. To update to a version of Ruby compiled against a viable version of OpenSSL, use the Mac Homebrew project: brew install ruby.

Once you have a brew's version of Ruby on your Mac, you can install NicInfo as a gem: /usr/local/opt/ruby/bin/gem install nicinfo.

After nicinfo is installed, find it in one of GEM PATHS shown in /usr/local/opt/ruby/bin/gem environment, in my case it is under /usr/local/lib/ruby/gems/3.2.0/, and I use /usr/local/lib/ruby/gems/3.2.0/bin/nicinfo --version to check if it works (it answered nicinfo 1.5.2).

For Windows 10 Pro users, Ruby can be installed using the Linux subsystem. Simply install it with apt install ruby. Then installe NicInfo as a gem: gem install nicinfo.

Other Windows system may use RubyInstaller.

Many Ruby managers exist to aid older Linux and Unix systems with the installation of multiple rubies. See the Ruby installation page here.

RedHat and CentOS distributions also have the Software Collections Libraries (SCL). More information on that is here.