Legacy to UEFI

I have a Biostar t5xe cfx-sli motherboard that does not seem to support UEFI. There is no option in BIOS to change from Legacy to UEFI. Biostar BIOS Flash Utility says I have the latest BIOS. Anything I can do without buying a new motherboard? Do I need UEFI? Do I need Windows 11 which requires UEFI?