system both in EFI mode and not at the same time

[Влад]

sda

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.3
ProcVersionSignature: Ubuntu 4.4.0-72.93-generic 4.4.49
Uname: Linux 4.4.0-72-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CasperVersion: 1.376.2
Date: Sun Apr 22 21:16:45 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 16.04 "" - Release amd64 (20170422)
ProcEnviron:
 LANGUAGE=ru_RU.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=ru_RU.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Strange. It seems to think your system is in EFI mode, but also not in EFI mode at the same time:

Apr 22 18:16:02 ubuntu ubiquity: System not running in EFI mode, not installing to EFI system partition.
Apr 22 18:16:02 ubuntu ubiquity: efibootmgr: EFI variables are not supported on this system.