This is not the correct answer: TPM20 was already working in Windows 10, no longer in Windows 11.
Microsoft silently made changes, ignoring the TPM specifications and passing secret commercial agreements with PC makers jsut to force people to buy new costly hardware (with new licences of Windows as well).
Microsoft has also decided to silently drop support of its own standard in Windows 10, and changed its own documentations at the same time. The world was taken by surprise (and now has to listen the lies of Microsoft, and breach of contract, even for existing supported versions of Windows).
The compatiblity check is hiding the real reasons, they are not at all based on technical reasons, just commercial ones. And worse:
Windows 11 is MUCH LESS secure now than Windows 10, e.g. Windows Defender will not longer be enabled and will no longer run from boot (you'll haver to reenable it after EACH reboot).
Microsoft seems to argue that these changes are good for users security, but the reality is that Microsoft is not adding, but dropping security features and support: many more PCs will be left without any effective protection (and soon without any support, even if customers paid for this).
microsoft is also lying when it says that it will upward compatible. This is completely FAKE. windwos 11 is only comptible with a limited set of hardware built by companies that made secret deals with a small branch Microsoft.
Even the Microsoft support teams were surprized. Even the most expensive and latest Surface Pro built and sold by Microsoft, are not eligible.
May be Microsoft should have kept its initial promiss (affirmed years ago and never demented since then, just very announced and never expected a few days ago, even if this version had many of these features tested under the name "Windows 10" and without ever saying that there would be compatibility restriction changes, that were never tested even by Insiders) : that windows 10 was the LAST major version of Windows and that it was now developing around the Linux kernel (or BSD, including Android, iOS and MacOS). What is the purpose of the Windows Insider program when there are so disturbing changes and Microsoft actually did not listen its participants or did not ask anything before doing such strong formal announcement and making radical changes in the documentation of ALL existing supported version of Windows)?
The result in a few months will be clear: Google, Oracle and Apple will capture the market abandonned by Microsoft, no customer can trust now Microsoft.
I see only good alternative: go to Linux (which are now equally capable, and have greats desktop environements).
The alternative woukld be that Google or Oracle will start selling their own version of Windows, running in a VM hosted on a Linux-based hypervisor and kernel).