laravel/octane#764 (comment)
As FrankenPHP has its own PHP, We can discard system level PHP install.
And start the app using./frankenphp php-cli artisan octane:start which will use Franky's built-in PHP to run the app.
But doing composer install requires PHP binary, so you still need a globally accessible PHP binary.
How about including composer to complement built-in php so doing ./frankenphp php-cli composer install would work seamlessly?