lubuntu installation fails on grub 16.10.

[Patrick J Seebauer]

New XMG laptop, supposed to be triple boot (Windows 10, ubuntu, other linux).
I have left some space for another Linux install and no swap (16G ram, but an ssd).
I suspect it is the efi partition, that I wanted to have grub on, but could not select Grub to be installed on it… (and couldn't select it to be mounted on /boot either).

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: ubiquity 16.10.14
ProcVersionSignature: Ubuntu 4.8.0-22.24-generic 4.8.0
Uname: Linux 4.8.0-22-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CasperVersion: 1.379
Date: Thu Dec 1 13:07:50 2016
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/lubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Lubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.1)
ProcEnviron:
 LANGUAGE=de_DE.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)