Yarn ERROR: There are no scenarios; must have at least one

It looks like that I was trying to execute the wrong yarn, because simply running sudo apt install yarn on my Ubuntu 18.04 gave me yarn from cmdtest.

So I solved by uninstalling it:

sudo apt remove yarn

And by installing it as the official website explains, which in my case (Ubuntu 18.04) it was the following:

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list

sudo apt update && sudo apt install yarn

yarn

You've got the wrong yarn. The yarn you're executing comes from the cmdtest package. Uninstalling cmdtest first should fix this:

sudo apt remove cmdtest

Once you've uninstalled it, run the commands below to install yarn properly:

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update
sudo apt install yarn

The real name you should use when installing is yarnpkg

sudo apt install yarnpkg

That is the solution.

Try this step by step. This worked for me.

sudo apt remove yarn
sudo apt install curl
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update
sudo apt install yarn