It is still available, but now in the advanced settings. In case you are interested in knowing the equivalent procedure for disabling update offers in Arduino IDE 2.x, here it is:
- 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:
- Select the "Preferences: Open Settings (UI)" command from the menu.
ⓘ You can scroll down through the list of commands to find it or type the name in the field.
A "Preferences" tab will open in the Arduino IDE main panel. - Type
arduino.checkForUpdatesin the "Search Settings" field of the "Preferences" tab. - Uncheck the box under the "Arduino: Check For Updates" setting.
- Close the Preferences tab by clicking its X icon.
