The WikibaseCirrusSearch extension requires the wikimedia-extra plugin for Elasticsearch, but this is barely documented anywhere: this code comment is the only place in the extension itself, I think.
//NOTE: needs the cirrus search wikimedia-extra plugin to be installed to work $config = [ 'type' => 'text', 'index_options' => 'freqs', 'analyzer' => 'extract_wb_quantity', 'search_analyzer' => 'keyword', ];
This is very confusing to users who try to set up CirrusSearch with vanilla Elasticsearch installs.