Software Updater prompts empty window to apply non-existing updates

[Benjamin Schmid]

The update-manager applications prompts to apply updates, but the list of updates is empty.
The UI claims that there are about 66MB to download. Yet the system is fully up-to-date.

Clicking "Install now" starts some work. Then the same window reappears

$ flatpak update
Looking for updates…
Nothing to do.
$ sudo snap refresh
Alle Snaps sind aktuell.
$ sudo apt full-upgrade
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut.
Statusinformationen werden eingelesen.... Fertig
Paketaktualisierung (Upgrade) wird berechnet... Fertig
0 aktualisiert, 0 neu installiert, 0 zu entfernen und 0 nicht aktualisiert.

Here is a terminal run of update-manager:

$ update-manager --debug
DEBUG:root:WARNING: can not get name for '<Gtk.TreeViewAccessible object at 0x7f626804cc80 (GtkTreeViewAccessible at 0x7f6254003f50)>'
DEBUG:root:WARNING: can not get name for '<Gtk.TextViewAccessible object at 0x7f626804ca40 (GtkTextViewAccessible at 0x1cb7e60)>'
DEBUG:root:WARNING: can not get name for '<Gtk.TreeSelection object at 0x7f6262fbf180 (GtkTreeSelection at 0x1e8b120)>'
DEBUG:root:WARNING: can not get name for '<Gtk.LabelAccessible object at 0x7f62680522c0 (GtkLabelAccessible at 0x1dee740)>'
DEBUG:root:cache aufs_rw_dir: /tmp/
DEBUG:root:Free space on /: 29665132544
DEBUG:root:Dir /usr mounted on /
DEBUG:root:Dir /var mounted on /
DEBUG:root:Free space on /boot: 137284608
DEBUG:root:Dir /var/cache/apt/archives mounted on /
DEBUG:root:Free space on /tmp: 12884418560
DEBUG:root:Free space on /home: 29665132544
DEBUG:root:Dir /tmp mounted on /tmp
DEBUG:root:fs_free contains: '{'/': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>, '/usr': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>, '/var': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>, '/boot': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6d30>, '/var/cache/apt/archives': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>, '/tmp': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6700>, '/home': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626ac0a580>}'
DEBUG:root:dir '/var/cache/apt/archives' needs '66648648' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>' (29665132544.000000)
DEBUG:root:dir '/var' needs '0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>' (29598483896.000000)
DEBUG:root:dir '/usr' needs '52428800' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>' (29598483896.000000)
DEBUG:root:dir '/boot' needs '50856216.6' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6d30>' (137284608.000000)
DEBUG:root:dir '/tmp' needs '5242880' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6700>' (12884418560.000000)
DEBUG:root:dir '/' needs '10485760' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>' (29546055096.000000)
DEBUG:root:dir '/tmp' needs '0.0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6700>' (12879175680.000000)
DEBUG:root:dir '/usr' needs '0.0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7f626abf6c10>' (29535569336.000000)
DEBUG:root:Snap core18 is installed
DEBUG:root:Snap gtk-common-themes is installed
DEBUG:root:Snap gnome-3-28-1804 is installed
DEBUG:root:Snap gnome-3-28-1804 is not tracking the release channel
DEBUG:root:WARNING: can not get name for '<Gtk.TreeViewAccessible object at 0x7f62680c6580 (GtkTreeViewAccessible at 0x196d410)>'
DEBUG:root:WARNING: can not get name for '<Gtk.TextViewAccessible object at 0x7f62680c6340 (GtkTextViewAccessible at 0x1c6b5c0)>'
DEBUG:root:WARNING: can not get name for '<Gtk.TreeSelection object at 0x7f62680c64c0 (GtkTreeSelection at 0x282c520)>'
DEBUG:root:WARNING: can not get name for '<Gtk.LabelAccessible object at 0x7f62680c6c00 (GtkLabelAccessible at 0x27708f0)>'

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: update-manager 1:20.04.10.6
ProcVersionSignature: Ubuntu 5.4.0-72.80-generic 5.4.101
Uname: Linux 5.4.0-72-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sat May 1 08:32:39 2021
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/usr/bin/fish
SourcePackage: update-manager
UpgradeStatus: Upgraded to focal on 2020-04-23 (372 days ago)