Ubuntu – Weird Thunderbird Uninstall Problem

In the original(your backup) .thunderbird directory there should be a file that is named with a bunch of random letters and/or numbers followed by .default. That is you profile that has all your data stored in it. in the screen shot below it is 5euxiyvw.default

Paste that file from the backup into the new .thunderbird directory. You will then need to open the profiles.ini file and edit the last line to match the name of the new directory. Here is a screen shot of the file in the above screenshot. As you can see the Path= file was edited to be Path=5euxiyvw.default

Then you should only have to save the file and start Thunderbird. Thunderbird will now be looking at the newly pasted file folder for your profile and you should have all the emails and folders that were saved locally when you backed up your .thunderbird directory. All the setting for the old profile should be the same as well.

• The stuff in /usr/share/app-install is actually part of the package app-install-data as you can see in the output of dpkg-query -S /usr/share/app-install/*thunderbird*.

• /var/lib/app-info is generated by or for the same package.

• /usr/share/icons/HighContrast/scalable/apps-extra/thunderbird-icon.svg is part of gnome-accessibility-themes.

• /var/lib/apt/archives/ contains package archive files you downloaded in the past via Apt and that haven't been cleaned out yet.

You can remove all of these without serious consequences because they're either

• program icons or launchers related to Thunderbird though not owned by Thunderbird packages or
• cache data that will be re-downloaded or regenerated on demand,

though I don't think it's wise to corrupt packages to free a few meagre kilobytes and inodes. If you want to clear the Apt archive either manually or automatically there are cleaner, more elegant ways to achieve that (which is a topic for a different question).