Xubuntu 18.04.2 - How to install a DEB by double-clicking that DEB, please?

In Ubuntu 16.04 based distros, when I double-clicked a DEB, usually Gdebi was started and it checked the dependencies.
Then I clicked the Install button within GDebi and the installation was performed.

Now, in Xubuntu 18.04.2, which is based on Ubuntu 18.04, this method doesn't work anymore
(probably, because gksu was abandoned in Ubuntu 18.04, I guess).
Instead of this, I double-click the DEB, GDebi starts, checks the dependencies, but when I click the Install button,
GDebi closes immediately, without any error message, without a password query or any hint about what's going on.

I know, I can install a DEB using the terminal, but I'm looking for the described method.
What can I do to make it work again, please?

What you're describing *should* still work in 18.04.

Try reinstalling gdebi with:

sudo apt-get --reinstall install gdebi

If that doesn't work, then do the following:

sudo dpkg -i filename.deb

and paste the output here.

Using...

sudo dpkg -i filename.deb

...in the terminal did work flawlessly, but actually, this isn't the problem.

The only thing that doesn't work is when I double-click a .DEB.
In that moment, GDebi is supposed to start, to check for dependencies and after clicking the Install button,
to perform the installation, after the password query.

Instead of this, GDebi is closing immediately, after the Install button was clicked.
There's no password query either.

Here*s the wanted output, btw.:

sudo dpkg -i tvbrowser_4.0.1-1_all.deb
(Reading database ... 189459 files and directories currently installed.)
Preparing to unpack tvbrowser_4.0.1-1_all.deb ...
Unpacking tvbrowser (4.0.1-1) over (4.0.1-1) ...
Setting up tvbrowser (4.0.1-1) ...
Processing triggers for gnome-menus (3.13.3-11ubuntu1.1) ...
Processing triggers for desktop-file-utils (0.23-1ubuntu3.18.04.2) ...
Processing triggers for mime-support (3.60ubuntu1) ...

Thanks. I get that the command line isn't the issue - I just wanted to see if it was dpkg that was causing the problem that was resulting in gdebi not doing what it was supposed to.

Did you reinstall gdebi as I suggested?

Once you've done that, let's try running gdebi from the command line and see if it produces any errors:

sudo gdebi package.deb

Yes, I reinstalled GDebi and this is the output

sudo gdebi tvbrowser_4.0.1-1_all.deb
Reading package lists... Done
Building dependency tree        
Reading state information... Done
Reading state information... Done

Digital TV Guide
 Themeable and easy to use TV Guide - written in Java.
Do you want to install this package? [y/N]:y
(Reading database ... 189459 files and directories currently installed.)
Preparing to unpack tvbrowser_4.0.1-1_all.deb ...
Unpacking tvbrowser (4.0.1-1) over (4.0.1-1) ...
Setting up tvbrowser (4.0.1-1) ...
Processing triggers for gnome-menus (3.13.3-11ubuntu1.1) ...
Processing triggers for desktop-file-utils (0.23-1ubuntu3.18.04.2) ...
Processing triggers for mime-support (3.60ubuntu1) ...

Right, a search on the web for gdebi closes immediately when install pressed turns up the following page (and similar ones):

https://bugs.launchpad.net/ubuntu/+s...i/+bug/1760910

What a mess. It certainly works fine in Mint 19.x, based on 18.04, and I'm surprised that if it's affecting all users of 18.04 that there hasn't been a bigger noise about it.

Anyway, the suggested fix in post #12 on that thread looks appealing (I use lxqt-sudo as well but for different purposes). Give it a go.

Originally Posted by hydrurga What a mess.

You're so absolutely right!
I definitely agree to that!
All of this just because gksu was abandoned.

Indeed, the package lxqt-sudo seems to fix it, but wow, this was quite a huge installation
(well maybe because I added the language pack lxqt-sudo-l10n as well).
Hopefully, this installation will not have any unexpected side effects.

Thank you very much.

Originally Posted by madmax25 You're so absolutely right! I definitely agree to that! All of this just because gksu was abandoned. Indeed, the package lxqt-sudo seems to fix it, but wow, this was quite a huge installation (well maybe because I added the language pack lxqt-sudo-l10n as well). Hopefully, this installation will not have any unexpected side effects.

Let us know if you do experience any, but I think that it is unlikely.

In essence, gdebi should have had a polkit policy added when gksu was removed. Why it hasn't been done in this case, or isn't configured correctly, I have no idea. Perhaps someone else can provide that info. But at least you have a working system.

You can mark the thread as "Solved" if you want (see "Thread Tools" at the top of this thread).

Originally Posted by hydrurga In essence, gdebi should have had a polkit policy added when gksu was removed.

Sounds like this is exactly the information, I'm looking for.

I think, I better wait for that, before I mark this thread as solved.

Maybe, there's somebody around, knowing what to do about this polkit policy?!