Hi,I was just bisecting this and noticed that EFI booting stops working if I simply rebuild both syslinux 3:6.04~git20190206.bf6db5b4+dfsg1-3 and gnu-efi 3.0.9-2.
If I rebuild only syslinux but use the gnu-efi package from the archive I can boot successfully. This seems to indicate the that the boot issue is not related to the new gnu-efi version but something different, possibly a change in the toolchain.
-Timo