What will happen if I install ELK stack with the unsupported version?

I've noticed that installed Elasticsearch cluster and Kibana was installed on Ubuntu 20.04 LTS. (By one of my colleague) with unsupported version 6.2.4 (from the Elastic Support Matrix | Elasticsearch).

But he said the Elasticsearch and Kibana both works perfectly also no Error show in log.

Now, I'm going to install Logstash that must connect with that Elasticsearch and Kibana and I have to install Logstash the same version 6.2.4 on the Docker but I still concern about the unsupported version. Not really sure if there are issues on the future ?.

The supported version start from 6.8.x. again, the dude one who install Elasticsearch tell me not to upgrade it cause it will definitely affect to many running jobs.

Well...no idea and experience for using unsupported version.

Any suggestions for this? should I go further ? ?