In version 8.1 namespaces in this package https://github.com/elastic/elasticsearch-php had been changed, so when I tried to update laravel version I received next error: Class "Elasticsearch\ClientBuilder" not found, - because now it is located in Elastic\Elasticsearch\ClientBuilder. Old namespaces style is still used in elasticsearch/elasticsearch v7.17, but it is not compatible with matchory/elasticsearch v3.
Please, check this and fix.