I tried something different - made a clone of the Windows 10 SSD on my main PC and installed it on a spare old PC of 2011 vintage, then downloaded the Windows 11 ISO from the MS download page. Once downloaded, I extracted the file/folder set, copied then opened in Notebook the appraiserres.dll file (situated in the Sources folder).

I then deleted all instances of TPM and UEFI and saved the copy back to the Sources folder.

Windows 11 then installed without deleting data and software!!