Please correct AVR board packages documentation

Development Tools IDE 2.x
7

It is this one in particular that you must delete in order to clear the stored flag that tells Arduino IDE it has already performed the first run installations:

Or if you want to be surgical about it, you can reset the flag in the database (which is stored under that folder):

  1. Press the Ctrl+Shift+P keyboard shortcut (Command+Shift+P for macOS users) to open the "Command Palette".
    A menu will appear on the editor toolbar:
    Command Palette screenshot
    Command Palette screenshot440×112 11.9 KB
  2. Select the "Toggle Developer Tools" command from the menu.
    ⓘ You can scroll down through the list of commands to find it, or type the command name in the field.
    The developer tools panel will open in the Arduino IDE window.
  3. Select the "Application" tab from the bar at the top of the developer tools panel.
  4. Select Local storage > file:// from the "Storage" section of the navigation subpanel at the left side of the developer tools panel.
    You will see a list of the entries in Arduino IDE's local storage database in the main developer tools panel.
  5. Type theia:initializedLibsAndPackages in the "Filter" field at the top of the main developer tools panel.
  6. Double-click on the true value under the "Value" column of the theia:initializedLibsAndPackages key.
  7. Type false.
  8. Press the Enter key.

Now if you restart Arduino IDE, or even open a new window, you will see it performs the first run installations of the "Arduino AVR Boards" platform (machine identifier arduino:avr) and the "Arduino_BuiltIn" library (and more importantly, that library's dependencies).