It sounds like your phone may indeed be hard bricked, especially if it's not responding to attempts to flash the stock firmware using SP Flash Tool. The fact that it only vibrates occasionally and doesn't display anything suggests that there may be a deeper hardware issue at play.
While it's possible that the LCD may be damaged and causing the lack of display, it's more likely that the issue is related to the internal components of the phone, especially considering that the phone doesn't even boot up or show any signs of life beyond the occasional vibration.
In this situation, it's important to consider the following troubleshooting steps:
1. Check the Battery: Make sure that the battery is properly connected and charged. A faulty battery connection or a drained battery could cause issues with the phone booting up.
2. Try a Different USB Cable and Port: Sometimes, using a different USB cable or port can help establish a better connection between the phone and the computer during the flashing process.
3. Check for Hardware Damage: Inspect the phone for any signs of physical damage or water damage that may be affecting its functionality. If you suspect any damage, it may be worth seeking professional repair services.
4. Seek Professional Help: If you've exhausted all DIY options and the phone still isn't responding, it may be best to take it to a professional repair technician or the manufacturer's service center for further diagnosis and repair.
In the meantime, if you have access to another similar phone, you could try using it to test the battery, display, or other components to help narrow down the possible causes of the issue with your bricked phone.
I hope this information helps, and I wish you the best of luck in resolving the issue with your phone!
PH