NSW Spatial Services have announced that the SIX Maps website is being retired and will be replaced by Spatial Digital Twin (SDT) Explorer. The website URL is SDT Explorer can be found here. https://portal.spatial.nsw.gov.au/explorer/index.html
SDT Explorer has all of the functionality of SIX Maps but with more function being added particularly with additional datasets that can be viewed.
I will be preparing some presentations on SDT Explorer shortly and provide information through the Society of Australian Genealogists Events program.