nominatim release-v3.1.0
It works as a standalone nominatim docker container and it should init to a working install, but it requires some tuning and configuration changes to suit your environment.
See https://github.com/chesty/maps-docker-compose for a full OpenStreetMaps environment using this image plus others.
To keep nominatim updated, start the nominatim-updatedb container every 24 hours.