For flashing stock ROMs on LG devices, the primary tool you'll want to use is the LG Flash Tool. Here’s a bit more information about it:

LG Flash Tool

• Features:
  • Supports various LG device models.
  • Allows you to restore devices to factory settings.
  • Can recover devices that are stuck in boot loops or bricked.
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Additional Tools

• LG UP: Another tool that can be used for flashing firmware, particularly for newer LG devices.
• LG Bridge: Primarily for updating and backing up LG devices, but also offers recovery options.
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Important Notes

• Always download the correct firmware for your specific device model.
• Ensure your device is adequately charged before starting the flashing process.
• Backup your data, as flashing will erase all existing data on the device.