Panel app disappeared; here;s how I fixed it.

Not so fast, amenex ...

On another Lenovo T420 running Trisquel_9, the panel got crossed up, so I tried
following my own advice, and invoked "Reset Panel."

Alas, the new panel appeared, but without any apps, contrary to previous
experience recounted above.

Adding "Indicator Applet Appmenu" produced the words, "no indicators."

That leaves this installation of Trisquel_9 with no WiFi connection, as hot
plugging the WiFi dongle freezes the system. Rebooting produces no magic, either.

How can I fix the Panel application ?

George Langford

"Panel" appears in my Add/Remove Applications; unchecking the adjacent box
produces the advice to remove/[repair] it with Synaptic Package Manager.

Never having used that before, I navigated to Synaptic Package Manager,
searched on the term, "Panel" and found nothing about Mate; that was in
Trisquel_9. There are several Mate packages in use on this Trisquel_9
installation.

In Trisquel_8, on the other hand, there is a Mate Panel package in the
Synaptic Package Manager.

Without a WiFi connection, am I forced to dig out a network cable and
upgrade Synaptic Package Manager ?

George Langford

Here's the good news: I have an Ethernet connection that's working.

The bad news is that trying to install mate-panel only made things worse.

Here's the saga:
sudo apt-get install mate-panel
...
Reading package lists... Done
Building dependency tree
Reading state information... Done
mate-panel is already the newest version (1.20.1-3ubuntu1+9.0trisquel9).
mate-panel set to manually installed.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
...
sudo apt-get remove mate-panel
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
bamfdaemon caja-eiciel caja-gtkhash caja-rename caja-seahorse gir1.2-bamf-3
gtkhash libb2-1 libbamf3-2 libcryptui0a libmateweather-common
libmateweather1 mate-applets-common mate-backgrounds
mate-indicator-applet-common mate-panel-common menu-xdg python3-psutil
python3-setproctitle python3-xlib seahorse-daemon
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
mate-applet-brisk-menu mate-applets mate-desktop-environment
mate-desktop-environment-core mate-desktop-environment-extras
mate-dock-applet mate-indicator-applet mate-panel mate-tweak trisquel
trisquel-recommended
0 upgraded, 0 newly installed, 11 to remove and 0 not upgraded.
After this operation, 4,916 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 342672 files and directories currently installed.)
Removing mate-applet-brisk-menu (0.5.0-7ubuntu1) ...
Removing trisquel-recommended (9.0-40) ...
Removing mate-applets (1.20.1-3) ...
Removing trisquel (9.0-40) ...
Removing mate-desktop-environment-extras (1.20.0+4+9.0trisquel1) ...
Removing mate-desktop-environment (1.20.0+4+9.0trisquel1) ...
Removing mate-desktop-environment-core (1.20.0+4+9.0trisquel1) ...
Removing mate-dock-applet (0.85-1) ...
Removing mate-indicator-applet (1.20.0-1) ...
Removing mate-tweak (18.04.16-1+9.0trisquel5) ...
Removing mate-panel (1.20.1-3ubuntu1+9.0trisquel9) ...
Processing triggers for desktop-file-utils (0.23-1ubuntu3.18.04.2+9.0trisquel1) ...
Processing triggers for libglib2.0-0:i386 (2.56.4-0ubuntu0.18.04.6) ...
Processing triggers for libglib2.0-0:amd64 (2.56.4-0ubuntu0.18.04.6) ...
Processing triggers for bamfdaemon (0.5.3+18.04.20180207.2-0ubuntu1) ...
Rebuilding /usr/share/applications/bamf-2.index...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for gnome-menus (3.13.3-11ubuntu1.1+9.0trisquel1) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for mime-support (3.60ubuntu1) ...
...
sudo apt-get install mate-panel
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
mate-panel : Depends: libmate-panel-applet-4-1 (= 1.20.1-3ubuntu1+9.0trisquel5) but 1.20.1-3ubuntu1+9.0trisquel9 is to be installed
E: Unable to correct problems, you have held broken packages.
...
sudo apt-get install 1.20.1-3ubuntu1+9.0trisquel9Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package 1.20.1-3ubuntu1+9.0trisquel9
E: Couldn't find any package by glob '1.20.1-3ubuntu1+9.0trisquel9'
E: Couldn't find any package by regex '1.20.1-3ubuntu1+9.0trisquel9'
...
sudo apt-get install libmate-panel-applet-4-1
Reading package lists... Done
Building dependency tree
Reading state information... Done
libmate-panel-applet-4-1 is already the newest version (1.20.1-3ubuntu1+9.0trisquel9).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

After more mucking about with Synaptic Package Manager, namely picking everything
remotely connected with Mate and the panel, the WiFi again came to life, surprisingly,
for both installations of Trisquel_9 on this Thinkpad T420.

The Ethernet cable came in very handy in the interim.

There appear to be no alternate ways of getting the WiFi up and running, other than
the questionably reliable Mate panel.

George Langford

Still mucking about.

Indicator Applet APPmenu no longer produces "No indicators;" now it's nothing at all.

There are no more Mate-panel programs or dependencies to install/reinstall.

What's to be done ?

George Langford