The public downloads provide links to the latest version. Naturally we keep a strict timeline of versions in our repository for customers which make special requests.
getting rid of backward compatibility
If you are referring to backward compatibility between version 6 and 3.5.0, the latter became legacy quite a while back, and the reason for dropping support for the NoMachine login is because we have over the years offered more and more authentication options in order to provide the most flexible and most secure integration with existing configurations available on the server host. Customers who have subscriptions with us can put in a special request to receive a download link to the earlier version if they are not able to update the server, or if they are still using NoMachine login even with version 5 (or 4). They can then distribute it to their users privately. Perhaps your administrator has already been in touch with us?
If you’re not sure, or you are the admin, please reach out to the Info team to request a download, https://www.nomachine.com/contact-request.