Installing a .deb package with all dependencies on Ubuntu or Debian can be done easily using the terminal.

Method 1: Using apt Command

1. Download the .deb file from a trusted source.
2. Open the terminal and navigate to the directory where the .deb file is located.
3. Use the dpkg command to install the package:
   

   sudo dpkg -i package-name.deb

Method 2: Using dpkg and apt-get

1. Download the .deb file from a trusted source.
2. Open the terminal and navigate to the directory where the .deb file is located.
3. Use the apt command to install the package and resolve dependencies:
   

   sudo apt install ./package-name.deb

4. After running dpkg, you might have missing dependencies. Fix them using apt-get:
   

   sudo apt-get install -f

Method 3: Using gdebi

1. First, install gdebi if it's not already installed:
   

   sudo apt-get install gdebi

2. Use gdebi to install the package and automatically resolve dependencies:
   

   sudo gdebi package-name.deb