fails to install on existing custom ESP of WNX Pro 18.04 GPT/UEFI Dual Boot

[Claudius Raphael Paeth]

Image is Ubuntu Desktop 18.04 LTS
written to USB 2.0 UFD via Gnome-Disks/Writer in Ubuntu Desktop 16.04.4 LTS

Custom partitioning

ESP offset=4MiB size=4512MiB(DVD-5) align=2MiB
WNX size=23552MiB(23GiB) align=2MiB Ntfs
LNX size=23552MiB(23GiB) align=2MiB Btrfs

repeatedly tried with all possible install-targets given in ubiquity (ESP/BIOSBOOT/LNX)
booted via BIOS/UEFI/CLOVER
doesn't make a difference if booted direct into ubiquity, or started from live

manual (grub-pc/grub-efi) install ain't problematic at all under given custom conditions

so i would point pinky to ubiquity, not grub-installer per se

this was the first time in 7 tries that bug-reporting actually proceeded/attempts to handle error automatically before stalled ubiquity to total halt/even killing by pid had no effect (as if it endlessly respawns immediately trying to start collecting dumps;

That should be it from here; as i have no idea how to debug in such a case and neither am willed to do right now;

For those that wonder about the alignment and offset; constant autocreation of full raw image dumps to udf 2.01 to DVD-SL-5-/BD-SL-25- -images, which is speed-up immense, in such a setting; Reason for the dumps is not of interest (here).

System is HP EliteBook 2740P Core-i5 2.53GHz VPro IronLake HD 8GiB 80GB Intel SSD with AMT/ME enabled and prepared for TXT Boot; Virtualization VT-d/EPT(IOMMU) and HyperThreading enabled, to allow nested virt boot of non-active os raw-vmdk/partition-boot with host-cpu-features shadowed.

Well, whatever; Feel free to sort it out or not. I'm done with probing ubiquity further and go on manually.

Oh, by the way: the keyboard detection/probing/guessing works as usual in subiquity, but ubiquity selects 104-key generic de, instead given 105-key de-nodeadkeys.

grub-pc:
  Installed: 2.02-2ubuntu8
  Candidate: 2.02-2ubuntu8
  Version table:
 *** 2.02-2ubuntu8 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

grub-efi:
  Installed: (none)
  Candidate: 2.02-2ubuntu8
  Version table:
     2.02-2ubuntu8 500
        500 cdrom://Ubuntu 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426) bionic/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

ubiquity:
  Installed: 18.04.14
  Candidate: 18.04.14.2
  Version table:
     18.04.14.2 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
 *** 18.04.14 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CasperVersion: 1.394
Date: Wed Jun 27 12:55:10 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)