Make sure to place composer's system-wide vendor bin directory in your $PATH so the laravel executable can be located by your system. This directory exists in different locations based on your operating system; however, some common locations include:
after running composer global require laravel/installer script, it downloads laravel/installer into ~/.config/composer/vendor. Thus to run next command, you need to add larael executable to the PATH, which is atm $HOME/.config/composer/vendor/laravel/installer/bin