I'm surprised that won't run the insider preview of Windows 11. My preview runs on VirtualBox the host is 10 years old, legacy bios 1st gen i5 750. Windows 10 (on the Dev channel) upgraded to Windows 11 without a problem, took a while though.
The latest build has just been applied today.
Have you been on the Dev channel for Windows 10 prior to 24th June? If not I'm sure you will get it later, but not sure what the way forward will be after the public release.