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Hello, after checking the ga-78LMT series motherboards support up to AMD Athlon II CPUs, and according to the Windows 11 support list in the documentation:Windows processor requirements Windows 11 supported AMD processors | Microsoft Learn, the minimum requirement is also up to Athlon III, for which I can basically deduce that your motherboard does not seem to be recommended and not suitable for upgrading to Windows 11, if you need If you need to use Windows 11, it is recommended that you replace your entire PC.
The support information I have searched for may not absolutely correct, so you can try contacting GIGABYTE for information on all suitable CPUs for this motherboard, then you can refer to the link above to compare and confirm if the hardware specification is supported by Windows 11.
If anything is unclear, please do not hesitate to let me know.
Best Regards,
Edward - MSFT | Microsoft Community Support Specialist