Laravel's pagination library ships with rendering engines or pagination presenters for Bootstrap 3 and 4. However 3 is enabled by default. Luckily, it's easy enough to switch. In AppServiceProvider::boot() add the following code:

// Add new namespaces:
use Illuminate\Contracts\Pagination\Paginator as PaginatorContract;
use Illuminate\Pagination\BootstrapFourPresenter;
use Illuminate\Pagination\SimpleBootstrapFourPresenter;
use Illuminate\Pagination\LengthAwarePaginator;
use Illuminate\Pagination\Paginator;

// code omitted

public function boot()
{
    // Change the ->paginate() presenter
    LengthAwarePaginator::presenter(function (Paginator $paginator) {
        return new BootstrapFourPresenter($paginator);
    });

    // Change the ->simplePaginate() presenter
    Paginator::presenter(function (PaginatorContract $paginator) {
        return new SimpleBootstrapFourPresenter($paginator);
    });
}

This will change the presenter used when you do Model::paginate(25)->render() or Model::simplePaginate(25)->render().