We've wrapped a Serbian stemmer into an Elasticsearch plugin (search/extra-analysis) and need to deploy the plugin so we can use the stemmer on Serbian-language wikis.
There are some additional prerequisites to the actual deployment.
Once the deployment is done, the next step—after the config that uses the plugin is also merged (in parent task T183015)—is to re-index, which will need a new ticket and to be listed in T147505.