Microsoft has already made the preview version of Windows 11 available for everyone. They have also clarified that even older systems, that do not fulfill all the requirements for upgrading to Windows 11, can also be upgraded to Windows 11. However, for such older systems, they are not going to provide any updates.
So if you are also thinking of installing Windows 11 on your old system, then you can create a bootable USB drive as the installation media for Windows 11. Then use this installation media to install Windows 11 on any PC you want.
There is a freeware tool called EaseUS Win11 Builder that helps you create a bootable USB media in just a matter of minutes. It will download all the files and prepare the media for you without the user having to worry about any of the commands or other things.
For creating a bootable USB Windows 11 installation media, you are going to need at least 8 GB USB pendrive. It is better to have a USB 3.0 pendrive because it will provide much faster file copying during the installation.
After attaching the USB pendrive to your PC, you can download and launch EaseUS Win11 Builder. It will detect your USB media and then you just have to click on the Create button. If you have multiple USB storage devices, then you should first select the correct target USB drive. There is also an option to bypass TPM requirement. This option is useful if your old system does not have any TPM chip.
It will take some time to download the installation files for Windows 11. The download is around 6 GB and it may take 10-20 minutes or more depending on your internet connection speed. After it has downloaded the required files, it will copy them to the USB drive and then make it bootable. You can then use this Windows 11 setup USB drive to boot into your PC and install Windows 11.
You can download EaseUS Win11 Builder from https://down.easeus.com/product/win11_builder.