updates - Stuck at point-release 14.04.4 (HWE upgrade path issue for 14.04.5 ?)

[ Ubuntu 14.04.4 desktop LTS with automatic updates enabled - boot with BIOS ]

When running:

$ sudo apt-get update
[normal output - no error]

$ sudo apt-get -y upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done

Calculating upgrade... Done
0 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.

$ sudo apt-get dist-upgrade
[same as above]

For reference:

$ uname -a

Linux HOSTNAME 3.16.0-50-generic #67~14.04.1-Ubuntu SMP
Fri Oct 2 22:07:51 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
$ lsb_release -a | grep -i descript
Description:    Ubuntu 14.04.4 LTS

I remain stuck at 14.04.4, the 2016-02-18 Trusty point-release.
My system is stable, but it won't budge from point-release version 14.04.4, and it's been weeks since I last got even a security update. Updates are installed from:

• Important security updates (trusty-security)


• Recommended updates (trusty-updates)


• Unsupported updates (trusty-backports)

"trusty-proposed" is off.

Packages are downloaded from the internet via:

• Canonical-supported free and open-source software (main)


• Community-maintained free and open-source software (universe)


• Proprietary drivers for devices (restricted)


• Software-restricted by copyright or legal issues (multiverse)

Mining the web for answers, I did find one instance of the same issue. I eventually got to one of the Trusty release-notes page. Quote:

By default, the 14.04.5 point release will ship with a newer 4.4 Linux

kernel from Ubuntu 16.04, and a matching X.org stack. This is based on
the 4.4.0 Extended Upstream Stable Kernel Release. The purpose of
providing a newer kernel in the 14.04.5 point release is for hardware
enablement.

and also:

Anyone wishing to opt into the hardware enablement stack for Trusty

may do so by running following command which will install the
linux-generic-lts-xenial and xserver-xorg-lts-xenial packages:

$ sudo apt-get install --install-recommends linux-generic-lts-xenial
xserver-xorg-core-lts-xenial xserver-xorg-lts-xenial
xserver-xorg-video-all-lts-xenial xserver-xorg-input-all-lts-xenial
libwayland-egl1-mesa-lts-xenial
and

The cmd yields:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package linux-generic-lts-xenial
E: Unable to locate package xserver-xorg-core-lts-xenial
E: Unable to locate package xserver-xorg-lts-xenial
E: Unable to locate package xserver-xorg-video-all-lts-xenial
E: Unable to locate package xserver-xorg-input-all-lts-xenial

E: Unable to locate package libwayland-egl1-mesa-lts-xenial

Posts [3],[4] (...) on the subject were not helpful, although in the latter @minerz029 recommends going to packages.ubuntu.com with a web browser to "Search package directories". Packages' availability results are:

• Package linux-generic-lts-xenial
  Exact hits:
  trusty-updates (kernel): Complete Generic Linux kernel and headers
  4.4.0.36.26: amd64 arm64 armhf i386 ppc64el




• Package xserver-xorg-core-lts-xenial
  Exact hits:
  trusty-updates (x11): Xorg X server - core server
  2:1.18.3-1ubuntu2.2~trusty3: amd64 arm64 armhf i386 powerpc ppc64el




• Package xserver-xorg-lts-xenial
  Exact hits:
  trusty-updates (x11): X.Org X server
  1:7.7+13ubuntu3~trusty2: amd64 arm64 armhf i386 powerpc ppc64el




• Package xserver-xorg-video-all-lts-xenial
  Exact hits:
  trusty-updates (x11): X.Org X server -- output driver metapackage
  1:7.7+13ubuntu3~trusty2: amd64 arm64 armhf i386 powerpc ppc64el





• Package xserver-xorg-input-all-lts-xenial
  Exact hits:
  trusty-updates (x11): X.Org X server -- input driver metapackage
  1:7.7+13ubuntu3~trusty2: amd64 arm64 armhf i386 powerpc ppc64el




• Package libwayland-egl1-mesa-lts-xenial
  Exact hits:
  trusty-updates (libs): implementation of the Wayland EGL platform -- runtime
  11.2.0-1ubuntu2~trusty1: amd64 arm64 armhf i386 powerpc ppc64el

All packages are available. And I am still stuck. I'd like to understand.

EDIT:
I also found

Not sure but it may point to one inconsistency in my setup. I run on kernel 3.16.0-50-generic which seems to correspond to release 14.10 and not to 14.04. Is this an upgrade path issue ? If so, how do I correct that ?

I change mirrors for package updates. Suddenly I had a pending update of 350 packages accumulated over the past 12 months.

An few minutes after completion of that first round I had several security update and about an hour later a point-release update to 14.04.5.

It looks like my old mirror had not been updating its vault in the past year or so.