You can install Sirius in exactly the same way you would Polaris, by burning the disk image to a microSD card using a program called Etcher running on another computer.
Built on top of the latest version of Raspbian (codenamed ‘Buster’), pi-topOS Sirius offers support for Raspberry Pi 4 which is at the heart of pi-top . However, you can also install it on pi-top  and pi-top CEED, as well as any stand-alone RPI 3B+ or above.
Our new operating system is available to download and install for free on our OS download page.
It's currently in beta, with the alpha release on track for a November launch alongside pi-top . As with all beta software there may be some issues so use with caution.