Did you install Xcode as indicated in the Macport installation documentation (https://www.macports.org/install.php)?

I thought it was installed, so I omitted it. My bad.
Looks like the installation went fine.
But in Terminal, when I run the command

auto-multiple-choice

-bash: auto-multiple-choice: command not found.

sudo port install auto-multiple-choice

Did you install needed fonts? Installation instructions are available in the wiki at Installing AMC on macOS.

Yes, I installed Linux Libertine font.
Not DejaVu font family or IPAexMincho and IPAexGothic fonts because I don't need Japanese.

The installation generate documentation in different languages and won't work if these fonts are not installed.

Thanks Joël
I have installed these fonts, but the same issue persists.

-bash: auto-multiple-choice: command not found

As the last installation of AMC failed, you have to try a new installation.

First some cleaning.

sudo port clean -f --ALL auto-multiple-choice

Then try again AMC installation

sudo port install auto-multiple-choice.

If the installation succeed, the command auto-multiple-choice should work.

Thanks Joël
But I get

sudo port clean -f --ALL auto-multiple-choice
Password:
Error: clean does not accept --ALL

Perhaps the option should be in lowercase.

sudo port clean -f --all auto-multiple-choice

Perfect.
It works now.
Thank you again Joël.