Elasticsearch is the most widely used tool for full-text search. Its development advances quickly and as a result, it has a relatively short life cycle.
Unless requested otherwise, we install the latest stable version by default. If you require an older version, please check its end of life date on the elasticsearch website.
When choosing a version, bear in mind, that Elasticsearch developers are not very invested in compatibility - new versions often have incompatible API and in order to update indexes, you usually need to do reindexation.