There are two fatals right now:
PHP Fatal error: Declaration of Drupal\snowball_stemmer\Plugin\search_api\processor\SnowballStemmer::getLanguageManager() must be compatible with Drupal\search_api\Plugin\search_api\processor\Stemmer::getLanguageManager(): Drupal\Core\Language\LanguageManagerInterface in /var/www/html/web/modules/contrib/snowball_stemmer/src/Plugin/search_api/processor/SnowballStemmer.php on line 102
PHP Fatal error: Declaration of Drupal\snowball_stemmer\Plugin\search_api\processor\SnowballStemmer::setLanguageManager(Drupal\Core\Language\LanguageManagerInterface $language_manager) must be compatible with Drupal\search_api\Plugin\search_api\processor\Stemmer::setLanguageManager(Drupal\Core\Language\LanguageManagerInterface $language_manager): Drupal\search_api\Plugin\search_api\processor\Stemmer in /var/www/html/web/modules/contrib/snowball_stemmer/src/Plugin/search_api/processor/SnowballStemmer.php on line 114
This happens on Search API 1.30 (https://git.drupalcode.org/project/search_api/-/commit/1205ca43095d6512a...)
Update Search API and clear the cache.
Remove these methods, because they are exactly the same. But we have to bump dependency to that version, otherwise it will break on installations with Search API < 1.30.
The other solution is to update these methods to be compatible with the Search API one.
Many thanks for catching that change in Search API and the patch. Bumping the required version should also work just fine.
Automatically closed - issue fixed for 2 weeks with no activity.