When downloading Unity for the first time, you will most likely install using the Unity Download Assistant.
If you choose to install Unity from the Download Assistant, you can proceed with this section and skip the next Install Unity from the Hub.
Please visit the Unity Download Archive and go to 2018.x, navigate to 2018.4.0f1, click the Download drop down menu for your platform, and select Unity Installer. Once the Download Assistant application is open, please follow these steps.
Click Continue in the Unity Download Assistant, until you see the Unity component selection.
In the Unity component selection window, make sure the following options are selected:
Android Build Support (*) (Not needed if you have an Android device.)
iOS Build Support (*) (Not needed if you have an iOS device.)
Windows Build Support (*) (Not needed if you're installing from Windows.)
Mac Build Support (*) (Not needed if you're installing from Mac.)
You will automatically be able to generate builds for the operating system you're currently installing from.
Click Continue until Unity is installed.