To install a specific version of the maatwebsite/excel package, you can specify the version number in the composer require command. For example, to install version 3.0, you can run the following command:
composer require maatwebsite/excel:3.0.*
This will install the latest version of the 3.0 branch. If you need a specific version within the 3.0 branch, you can specify it like this:
composer require maatwebsite/excel:3.0.0
If you need an alternative package for Laravel 5.7 and PHP 7.3, you can try the spatie/laravel-excel package. It provides similar functionality to maatwebsite/excel and supports Laravel 5.7 and PHP 7.3. You can install it with the following command:
composer require spatie/laravel-excel