1. If I install KDE Neon from scratch then at some point installer reboots without asking or showing any message. Newly installed system boots just fine, but it has cdrom in /etc/apt/sources.list uncommented so `apt get` requires to provide it. That's why I suppose that installation wasn't finished gracefully.

2. Sometimes during `sudo apt upgrade` during grub installations my system reboots without asking and sometimes it doesn't boot after restart (so I have to resort to recovery).
I've created a ticket here: https://bugs.kde.org/show_bug.cgi?id=383126

My system is a UEFI-enabled Samsung R730 notebook from 2010, so its UEFI may be of early version.

WHAT I WANT: how to record logs of Neon installer which I may post to the KDE bug reporter?

So the installer is ubiquity, it keeps logs in /var/log/installer, but I guess they don't survive reboots.
I need to somehow remount this folder to other persistent media (like other usb drive).