how to install telnet on macOS High Sierra ?

Hello. I use a Zyxel ZY-AMG1001-T10A modem to connect to the internet and need to use some arcane command line to configure it and to request DSL line-state information from the modem.

The Zyxel modem is quite recent. However, its command line interface requires using telnet port 23. Secure connection with ssh is not an option.

So I want to use my mac to issue commands to the modem by telnet across my private network to its LAN side.

How can I install telnet on my startup dive under macOS High Sierra ?

I am in process of installing xcode on the mac. That could not hurt. I have found on the internet references to solutions involving Homebrew or other similar packages, and also a reference to an insecure download from http://ftp.gnu.org.

Can I find secure installers somewhere ? TIA