Since UBCD 5.3.6 is a hybrid ISO, you can write it to USB using:
Version is particularly notable because it represents the final, most stable release of the classic UBCD legacy line before development shifted toward UBCD for Windows (which requires a separate Windows license). Download Ultimate Boot CD 5.3.6 - ALLPCWorld
If you find that UBCD 5.3.6 does not recognize your new hardware (e.g., NVMe drives or modern UEFI-only laptops), consider these alternatives: Since UBCD 5