error when installing

[tonygreis]

$ composer require spatie/laravel-backup
Using version ^6.8 for spatie/laravel-backup
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 2 installs, 0 updates, 0 removals

• Installing spatie/db-dumper (2.15.3): Loading from cache
• Installing spatie/laravel-backup (6.8.1): Loading from cache
  spatie/laravel-backup suggests installing laravel/slack-notification-channel (Required for sending notifications via Sla
  ck)
  Writing lock file
  Generating optimized autoload files

Illuminate\Foundation\ComposerScripts::postAutoloadDump
@php artisan package:discover --ansi

Illuminate\Contracts\Container\BindingResolutionException

Target [Spatie\Backup\Tasks\Cleanup\CleanupStrategy] is not instantiable while building [Spatie\Backup\Commands\Cleanu
pCommand].

at C:\xampp\htdocs\laravel\vendor\laravel\framework\src\Illuminate\Container\Container.php:982
978| } else {
979| $message = "Target [$concrete] is not instantiable.";
980| }
981|

982| throw new BindingResolutionException($message);
983| }
984|
985| /**
986| * Throw an exception for an unresolvable primitive.

1 C:\xampp\htdocs\laravel\vendor\laravel\framework\src\Illuminate\Container\Container.php:816
Illuminate\Container\Container::notInstantiable("Spatie\Backup\Tasks\Cleanup\CleanupStrategy")

2 C:\xampp\htdocs\laravel\vendor\laravel\framework\src\Illuminate\Container\Container.php:261
Illuminate\Container\Container::build("Spatie\Backup\Tasks\Cleanup\CleanupStrategy")
Script @php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 1

Installation failed, reverting ./composer.json to its original content.

[j5k]

Same here with newest Homestead and updated composer packages.

[j5k]

I fixed it with the following commands:
rm -rf vendor/* \n
git clean -ifx (deletes some caches, etc.)
composer update
composer require spatie/laravel-backup

Maybe an artisan cache cleaning is the key hint