rails webpacker:install Yarn not installed. Please download and install Yarn from https://yarnpkg.com/lang/en/docs/install/ code example

Example: ubuntu install yarn

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