Since there is no "OS Selector 2021," you must install it through .

: Tools like VMware or VirtualBox allow you to run multiple OSs simultaneously without needing a boot-level selector. Key Technical Limitations

The original OS Selector was designed for MBR (Master Boot Record) disks and older BIOS systems. Modern computers use UEFI, which handles multi-booting differently, making the old OS Selector obsolete.