How to install Unity3D on Ubuntu 18.04?

Unity3D is being released via a "Download Helper" now. Instructions to use it are as follows:

1. Head to the Unity-on-Linux Release Thread and go to the last page. The last post will contain the latest release. As of the time of this posting, that's this one. Download it.
2. Make that download executable. For example, chmod +x UnitySetup-2018.2.7f1

3. Install the prerequisites via

   sudo apt install libgtk2.0-0 libsoup2.4-1 libarchive13 libpng16-16 libgconf-2-4 lib32stdc++6 libcanberra-gtk-module
   

4. Run the installer.

   ~/Downloads/UnitySetup-2018.2.7f1
   

5. I like to place it in the /opt folder once it's installed and create a link so that I can launch it from the command line.

   cd
   sudo mv Unity-2018.2.7f1 /opt/Unity3D
   sudo ln -s /opt/Unity3D/Editor/Unity /usr/bin/unity3d
   

Once that's done, you can type unity3d to launch the Unity3D Editor.

The preferred way of installing Unity on Linux is by first installing Unity Hub.

Unity Hub setup file:

https://public-cdn.cloud.unity3d.com/hub/prod/UnityHub.AppImage

You can install the prefered version of Unity in the Installs section of Unity Hub application. It will automatically download and install it for you.

Source:

https://www.linuxdeveloper.space/install-unity-linux/

The last .deb version was actually Unity 2017.2.1f1. After that all the other version came in as .sha extension. .deb version actually automatically installs all the required dependencies. But now you have to install the dependencies on your own first.

Install the dependencies

sudo apt install gconf-service lib32gcc1 lib32stdc++6 libasound2 libc6 libc6-i386\
libcairo2 libcap2 libcups2 libdbus-1-3 libexpat1 libfontconfig1 libfreetype6 libgcc1\
libgconf-2-4 libgdk-pixbuf2.0-0 libgl1-mesa-glx libglib2.0-0 libglu1-mesa libgtk2.0-0\
libnspr4 libnss3 libpango1.0-0 libstdc++6 libx11-6 libxcomposite1 libxcursor1\
libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxtst6 zlib1g debconf npm

I also recommend installing build essentials

sudo apt install build-essential 

After that go to this link Unity on Linux: Release Notes and Known Issues - Unity Forum

Click on .html download links of the Unity version you want and select Linux download assistant.

After it is installed you can simply double click the setup file or run that using command line by:

cd Downloads
./UnitySetup*