Just to add a little note:
I do not have a TPM module but my motherboard does have a TPM 2.0 header. As an experiment I downloaded and ran the Windows 11 compatibility checker (updated and latest version from the Windows insider program) yesterday.
With the TPM disabled in BIOS the checker said my PC would run Windows 11 but there was an amber flag next to the TPM. I then enabled TPM in BIOS and ran the tool again. this time it said everything was OK.
So, from this I would think that, at the moment, the hardware has to be TPM capable for Windows 11 but, that you don't have to have an actual TPM Module physically installed.
The big problem is that Microsoft have not made any clear statements and have muddied the waters by their knee jerk reactions, when questions have been asked. Even the original compatibility checker had to be taken offline, soon after they released it, as it was not working correctly and failed too many capable machines. How are we supposed to know what is going to work if even Microsoft, at this late stage, don't!