Logstash 8.4.3 is not compatible with Elasticsearch 7.10, the last Logstash that is compatible with 7.10 is version 7.17, but there is a catch.
The elasticsearch output on any Logstash higher than 7.12, if I'm not wrong, will check if the Elasticsearch has a Elastic license, free or paid, they won't work with Elasticsearch 7.10 OSS or any fork like OpenDistro/Opensearch.