Unity 2019.4 is an LTS release, containing features released in 2019.1 to 2019.3, and is supported for 2 years. See the LTS release page for other available LTS installers.
Follow the links below to find User Manual pages on new and updated features in Unity 2019. These search links list new or updated User Manual pages in each Tech release, detailing the following:
If you are upgrading existing projects from an earlier version of Unity, read the Upgrade Guides for information about how your project may be affected. Here are the LTS specific upgrade guides: