This article discusses mainboard TPM 2.0 hardware support for Windows 11. For upgrade instructions from Windows 10 to Windows 11, review the following article: https://stefanos.cloud/upgrade-to-windows-11/.
Mainboard TPM 2.0 hardware support
Many Windows 10 PC owners these days are looking for ways to upgrade their PC to Windows 11. One mandatory preparation step is to ensure there is support for the Trusted Platform Module (TPM) version 2.0. If you don’t have a fairly recently bought mainboard, then chances are that you either need to flash your BIOS to latest firmware update and enable TPM 2.0 in your mainboard or add a TPM 2.0 card into your existing mainboard (example for Gigabyte motherboards is shown on this page: https://www.gigabyte.com/Motherboard/TPM-Card). If your mainboard is so old that it cannot even support TPM 2.0 cards, then most likely you will need a new mainboard.

In any case, you should research your mainboard manufacturer documentation for a mainboard and BIOS/UEFI firmware compatibility list with TPM 2.0. For example, in the case of Gigabyte mainboards, the following resources are available:
Last but not least, always check the Windows 11 upgrade specifications and system requirements (https://www.microsoft.com/en-us/windows/windows-11-specifications) before proceeding with any machine upgrades or new purchases.
As an example case study which can be used for reference, I consulted Gigabyte motherboard technical support team and received the following useful feedback.
To support Windows 11 the MB need to support Hardware TPM 2.0 or software TPM. On actual AMD and actual Intel chipset motherboards first check if the CPU supports SW TPM. If your CPU supports SW TPM Option, you will find this option in your Bios
Intel: Intel Platform Trust Technology ( PTT )
AMD: AMD CPU fTPM
The required TPM2.0 module can be found in the Mainboard specification paragraph Internal I/O Connectors or in the motherboard support lists of GIGABYTE TPM 2.0 modules: https://www.gigabyte.com/eu/Search?kw=GC-TPM2.0#Products-2-1
Before buying a TPM Module please check on Microsoft processor support list, if your processor does meet the Windows 11 requirements:
Intel – Windows Processor Requirements Windows 11 Supported Intel Processors | Microsoft Docs
AMD – Windows Processor Requirements Windows 11 Supported AMD Processors | Microsoft Docs
Sources
https://www.gigabyte.com/webpage/20/HowToReflashBIOS.html