telnet and ftp have been removed from Mac. While people shouldn’t be using insecure versions of
these protocols, I use telnet often to diagnose connections issues. The solution to this is to install
inetutils.

You can install inetutils using Homebrew or MacPorts, but I prefer compiling from source. It is more
straight-forward and does not require installing additional packages.

dowload your preferred version of inetutils from https://ftp.gnu.org/gnu/inetutils/.

curl https://ftp.gnu.org/gnu/inetutils/inetutils-1.4.0.tar.gz -o inetutils-1.4.0.tar.gz
tar xzvf inetutils-1.4.0.tar.gz

Compile and install inetutils.

cd inetutils-1.4.0
./configure
make
sudo make install