Backupper LiveCD works for Legacy BIOS but not for UEFI

In the past I created a Aomei Backupper LiveCD (ISO) from an installed Backupper Pro software (under 64bit Win7 with legacy BIOS).

When I put this ISO onto a 32GB USB Flash Drive and booted this tool on a computer with Legacy-BIOS then everything works fine.
However when I plugin the same USB flash Drive on another computer (which allows NO Legacy BIOS but offers only UEFI) and boot it then
the USB flash drive is NOT recognized in Boot Menu.

Why not?

I used the famous, wide spread Rufus tool v3.5 to install the ISO onto the USB flash drive.
Yes, Secure Boot is disabled in the computer (only UEFI is aktive).

Do I have to specify already at ISO creation time (=in Aomei Backupper) the target BIOS type (legacy or UEFI)?

Is there no multi-BIOS-type ISO creation in Aomei Backupper?

Can I somehow find out inside the Backupper ISO (without booting it) if its for Legacy BIOS or UEFI ?

Thank you