Missing instructions for multi-use of Elasticsearch installation

[alxhu-dev]

In the Elasticsearch page (section "Choosing the correct preset") is this information:

If you have multiple Mastodon servers on the same machine, and you are planning to use the same Elasticsearch installation for all of them, make sure that all of them have unique REDIS_NAMESPACE in their configurations, to differentiate the indices. If you need to override the prefix of the Elasticsearch indices, you can set ES_PREFIX directly.

But when you visit the configuration page (section "Redis"), there is this information for REDIS_NAMESPACE:

This option is deprecated. Sidekiq 7 removes support for namespaces, and so will a future version of Mastodon. We will attempt to document a clear migration path by the time that happens. If you are setting up a new instance, using this option is highly discouraged.

If I want to setup multiple instances which use the same Elasticsearch installation, there is no clear instruction on how to accomplish this because the usage of REDIS_NAMESPACE is highly discouraged, but no alternative has been offered.