I filed a bug at the wrong place.. They recommended it is a KDE neon-specific issue.

It happens when upgrading postgres.

https://bugs.launchpad.net/ubuntu/+sour ... ug/1853468

* eddieloveskde copy pastes:

bug Description: Setting up postgresql-common (190ubuntu0.1) ... gives (on package upgrade)
supported-versions: WARNING! Unknown distribution: neon

urgh, though Linux KDE NEON is a well known distribution.

Add tags Tag help
someone wrote

190ubuntu0.1 suggests that you are on Ubuntu bionic or something derived from that.

The package needs to know where it runs, and it does so via /etc/os-release

# we have /etc/os-release, use it
if [ -r /etc/os-release ]; then
. /etc/os-release
DISTRO="${ID:-unknown}"
RELEASE="${VERSION_ID:-unstable}" # unstable doesn't have this field

Based on that in /usr/share/postgresql-common/supported-versions there is a mapping which default now applies.
That could for example be
DISTRO=Ubuntu
RELEASE=18.04

Which would map to postgresql 10.

In your case that isn't true. You are not running Ubuntu but a derivative.
If that decides to change these values then packages might stumble over that.
There is nothing to fix here, it is part of KDE-Neon as a downstream to maintain a Delta for this just as Ubuntu does to Debian and Debian does to upstream.

Changed in postgresql-common (Ubuntu):
status: New → Invalid

oh forgot to mention the AND pkcon part...

https://bugs.kde.org/show_bug.cgi?id=414368

they say: pkcon is part of PackageKit (not a kde project) ..

I can understand that:
BUT: trying to report an issue for Distribution KDE Neon .. and pkcon is its package manager.
and it fails when a network interface is not managed by Network-Manager....
Maybe someone can look at source-code of pkcon and adjust it to use the network interfaces and routes.

https://snapcraft.io/install/postgresql10/kde-neon
https://packages.ubuntu.com/bionic-upda ... 0/download
https://www.postgresql.org/download/linux/ubuntu/
I have no idea. I haven't touched anything Ubuntu for quite some time now. Moreover, I'm not a huge fan of PakageKit. I use APT, dpkg and debs. Hope it helps.