Feature request: Add UEFI and Ventoy support

[EricB1978]

Hello, and thank you very much for maintaining Linux Live Kit. It is a great project, and many of us truly appreciate your work.

Currently, the generated ISOs only provide legacy BIOS boot. On modern hardware, we need UEFI boot support. At the moment, the workaround is to manually rebuild the ISO using xorriso with options like:

xorriso -as mkisofs -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin
-c boot.cat -b isolinux/isolinux.bin -no-emul-boot -boot-load-size 4
-boot-info-table -eltorito-alt-boot
-e EFI/BOOT/BOOTX64.EFI -no-emul-boot -isohybrid-gpt-basdat
-o output-uefi.iso input-dir/

This process adds the EFI boot image (typically EFI/BOOT/BOOTX64.EFI) and ensures GPT/MBR hybrid structure. It would be very helpful if Linux Live Kit could handle this directly, so that ISOs are immediately bootable on both BIOS and UEFI systems without manual modification.

In addition, Linux Live Kit ISOs are not always recognized by Ventoy (https://www.ventoy.net/en/index.html). Ventoy expects ISOs to include proper El Torito UEFI boot entries and GPT hybrid support. According to Ventoy’s UEFI ISO booting documentation (https://www.ventoy.net/en/doc_uefi.html), the ISO must:

• Contain a valid \EFI\BOOT\BOOTX64.EFI (and BOOTIA32.EFI for 32-bit if needed).
• Include correct El Torito boot catalog entries for both BIOS and UEFI.
• Be built with isohybrid --uefi or equivalent (xorriso options).

Why this matters:

• UEFI support is mandatory for modern PCs, laptops, and servers (many ship without legacy/CSM support).
• Ventoy is widely used to manage multiboot USB sticks, especially by sysadmins and testers. Having Linux Live Kit ISOs work out-of-the-box with Ventoy would save time and make the tool much more accessible.
• Linux Live Kit is CLI-based, which makes it perfect for automation. Unlike GUI tools such as CUBIC, Linux Live Kit allows creating ISOs directly from the command line. For example, with a simple cron job, one could generate a fresh ISO automatically every day — which is currently impossible with CUBIC.

Suggestions / possible approaches:

1. Integrate GRUB2 EFI binaries (grubx64.efi, grubia32.efi) into the ISO build process.
2. Add isohybrid --uefi (from syslinux-utils) or equivalent xorriso -as mkisofs options when generating the ISO.
3. Ensure the ISO has both BIOS and UEFI El Torito entries (-b isolinux/isolinux.bin for BIOS and -e EFI/BOOT/BOOTX64.EFI for UEFI).
4. Test the generated ISO under Ventoy (latest version) to confirm direct boot works without manual modification.

Reference links:

• Xorriso: https://www.gnu.org/software/xorriso/
• Ventoy project: https://www.ventoy.net/en/index.html
• Ventoy UEFI requirements: https://www.ventoy.net/en/doc_uefi.html

Thank you again for your great work and for considering this feature request. Adding native UEFI + Ventoy compatibility would make Linux Live Kit much more powerful, user-friendly, and suitable for automated workflows.