You can download Manticore first release from https://manticoresearch.com/downloads/.
Manticore 2.3.3 is a transition release from Sphinx 2.3.2-beta. It contains only branding changes, no few features or fixes.
We will announce soon when the next version will be build and how often we plan to package new releases.
In the mean time, you can compile latest Manticore from the github repository, which already has several new small features.
The official documentation is up-to-date with the latest code.