Syslinux - Dec 2020 - Both UEFI+BIOS USB and multisystem

Hello all.

I'm trying to make a USB bootable with UEFI and BIOS and with many
systems on in.

I'm using a USB with 3 partitions: first of type EF02, second type EF00
and third is type 8300 with a unzipped Debian. I've installed gptmbr.bin.

I can boot in a BIOS only machine, and in a newer machine without CMS
active.

I'm having problems when I try to launch syslinux.cfg in third
partition, I'm using chain.c32 with "boot,2" in APPEND, but it
seems
doesn't go to the partition and seems start configuration in second
partition. I'm not sure if is possible ot chainloading to a Linux type
from an EFI (FAT32) partition.

Regards and thanks in advanced

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> I'm having problems when I try to launch syslinux.cfg in third
> partition, I'm using chain.c32 with "boot,2" in APPEND, but
it seems
> doesn't go to the partition and seems start configuration in second
> partition. I'm not sure if is possible ot chainloading to a Linux type
> from an EFI (FAT32) partition.
If you are trying to chain to the "third" partition, it is not clear 
why you would use "boot,2". Perhaps some of the partitions you 
described are not actually counted / present / seen?

Moreover, it is not clear if you are saying that whatever you are using 
in syslinux.cfg is all working correctly and as expected for BIOS, and 
that is only partially failing for UEFI in some particular scenario(s). 
Or, instead, perhaps you mean that "chain.c32 boot,2" is failing in 
both, BIOS and UEFI boot modes. Or...

At any rate, it seems that you need to actually read some 
documentation. For example:

* EF02 is required by GRUB2; 
* chain.c32 6.04-pre1 is for BIOS (and/or CSM) only, not for UEFI; 
* syslinux.efi 6.04-pre1 is not capable of loading anything other than 
a Linux kernel that: 
** is already compatible with UEFI and, 
** that it is located in the same ESP partition as syslinux.efi.

Regards,
Ady.