The conversation with "su" has failed

[jlittle]

That looks like software-properties. To could try

$ sudo -i
[sudo] password for john:
$ software-properties-qt

[Supersayano]

That looks like software-properties. To could try

Of course, this is the console output to your commands:

julio-cesar@mi-equipo:~$ sudo -i
[sudo] contraseña para julio-cesar:    
root@mi-equipo:~# software-properties-qt
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
root@mi-equipo:~#

And that opened the attached screenshot window.

I can open "software-properties" from its launcher, and I can also open the driver manager from the console. The problem is that when I open certain applications such as "Grub Customizer" from its launcher, or the driver manager from the system preferences, the dialog window where it asks for the password gives an error of "The conversation with "su" has failed" as shown in the screenshot of my first message in this thread.
Thanks and regards...

[jlittle]

Sorry, now I get it... "The problem is that when I open certain applications ... the dialog window where it asks for the password gives an error".

I suggest check for environment variables that may be affecting su. Also, the su man page refers to some files, perhaps they have been changed; however, I don't know a good way to check them.

[Supersayano]

How are these environment variables verified?.

Well, it seems like I have an unsolvable problem. This was my last letter, so I guess if no one here can help me no one will.
Thank you all for your help and greetings...

[Snowhog]

Wasn't offered, and we didn't ask, but is this happening on a 'new' installation of Kubuntu 24.04, or an upgrade from an earlier version of Kubuntu?

[Supersayano]

It is a fresh installation of Kubuntu 24.04. I previously had 18.04 for many years, but that was on another computer.

During the first days since its installation this problem did not exist, and it was one day when it suddenly started to happen and I don't know why.
Greetings...

[Snowhog]

At anytime after the new installation, when this issue wasn't happening, did you launch any GUI application (and use it) from the CLI using sudo?

[Supersayano]

I'm not sure, but i think so. Thinking a little, I think it was almost certainly Kate, although I don't even remember why I did it. Or maybe it was Dolphin, I don't really remember, but it's possible.
Greetings...

[Snowhog]

Open Konsole. Verify you are in your users home directory (you should be). Type: ls -la * | grep root and press Enter. You should get nothing returned; just your prompt. But if you do, copy the output and paste it here in your reply.

[Supersayano]

This is what the console returns to that command:

julio-cesar@mi-equipo:~$ ls -la * | grep root
-rwsr-xr-x  1 root        root            50672 abr 28  2022 chrome-sandbox
julio-cesar@mi-equipo:~$

Greetings...

[Snowhog]

So one item in your users home directory is owned by root. No files or folders inside ones home directory should be owned by root. Are you using Chrome as your browser?

As nothing in ones home directory should be owned by root, let's change that ownership. In the konsole, and still in your home directory, type: sudo chown julio-cesar:julio-cesar chrome-sandbox and press Enter.

[Supersayano]

I do use the Chrome browser, although my main browser is Firefox.
In the user folder there is no directory called chrome-sandbox.
This is the console output to your command:

julio-cesar@mi-equipo:~$ sudo chown julio-cesar:julio-cesar chrome-sandbox
[sudo] contraseña para julio-cesar:     
chown: no se puede acceder a 'chrome-sandbox': No existe el archivo o el directorio
julio-cesar@mi-equipo:~$

Greetings...

[Snowhog]

The output in post #25 says otherwise. When you open Konsole, you should be in your users home directory. In the konsole, type: pwd and press Enter. Do you get /home/julio-cesar as the output? If 'yes', then type: ls -la and press Enter. Copy and paste it here in your reply.

[Supersayano]

Please believe me when I tell you that such a directory does not exist.

julio-cesar@mi-equipo:~$ pwd
/home/julio-cesar
julio-cesar@mi-equipo:~$ ls -la
total 892
drwxr-x--- 54 julio-cesar julio-cesar   4096 jun  5 19:14  .
drwxr-xr-x  3 root        root          4096 may  8 16:54  ..
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may 20 21:14  .adobe
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may 12 01:41  .afirma
drwxrwxr-x 10 julio-cesar julio-cesar   4096 may  3 12:36  AIMP
drwxrwxr-x  2 julio-cesar julio-cesar   4096 jun  6  2023  .anydesk
-rw-rw-r--  1 julio-cesar julio-cesar    102 may 10 03:39  .apport-ignore.xml
drwxrwxr-x  4 julio-cesar julio-cesar   4096 jun  5 18:47  Avidemux
drwxrwxr-x  4 julio-cesar julio-cesar   4096 jun  5 19:14  .avidemux6
drwxrwxr-x  4 julio-cesar julio-cesar   4096 may 30 14:42  balenaEtcher
-rw-------  1 julio-cesar julio-cesar   3099 jun  5 18:57  .bash_history
-rw-r--r--  1 julio-cesar julio-cesar    220 mar 31 10:41  .bash_logout
-rw-r--r--  1 julio-cesar julio-cesar   3771 mar 31 10:41  .bashrc
drwxrwxr-x 57 julio-cesar julio-cesar   4096 jun  5 19:14  .cache
drwxrwxr-x  6 julio-cesar julio-cesar   4096 ago 20  2023  Cloudflare
drwx------ 51 julio-cesar julio-cesar   4096 jun  5 19:14  .config
drwx------  3 julio-cesar julio-cesar   4096 jun  3 13:22  .dbus
drwxrwxr-x  6 julio-cesar julio-cesar   4096 abr 28  2022  Deemix
-rw-------  1 julio-cesar julio-cesar    102 may 19 00:11  .directory
drwxr-xr-x  2 julio-cesar julio-cesar   4096 jun  5 18:57  Escritorio
-rw-r--r--  1 julio-cesar julio-cesar  23910 abr 19 21:30  .face
lrwxrwxrwx  1 julio-cesar julio-cesar      5 abr 19 21:30  .face.icon -> .face
drwxrwxr-x  2 julio-cesar julio-cesar   4096 may 24 13:42  .filezilla
drwxrwxr-x  7 julio-cesar julio-cesar   4096 jun  5 14:10  firefox
drwxrwxr-x  2 julio-cesar julio-cesar  20480 mar 15 16:38  .fonts
-rw-rw-r--  1 julio-cesar julio-cesar    529 may  8 22:27  .fonts.conf
drwxr-xr-x  4 julio-cesar julio-cesar   4096 jun  5 18:57  FreeFileSync
drwxrwxr-x  3 julio-cesar julio-cesar   4096 jun  5 18:59  Gifcurry
drwxrwxr-x  5 julio-cesar julio-cesar   4096 may 12 02:35  GL-Z
-rw-rw-r--  1 julio-cesar julio-cesar    278 jun  5 19:14  .gtkrc-2.0
drwx------  2 julio-cesar julio-cesar   4096 jun  3 13:22  .gvfs
drwxr--r--  2 julio-cesar julio-cesar   4096 may 12 02:47  .hardinfo
drwxrwxr-x  2 julio-cesar julio-cesar   4096 may 29 20:35  iconos
drwxrwxr-x  8 julio-cesar julio-cesar   4096 may  8 19:54  .icons
-rw-rw-r--  1 julio-cesar julio-cesar     84 may 10 23:16  .install4j
drwxrwxr-x  2 julio-cesar julio-cesar   4096 ago  7  2023  JAP
-rw-rw-r--  1 julio-cesar julio-cesar  87092 may 12 03:01  .jap.conf
drwxrwxr-x  4 julio-cesar julio-cesar   4096 may  9 19:29  .java
drwxrwxr-x 17 julio-cesar julio-cesar   4096 may 22 12:58  jd2
-rw-------  1 julio-cesar julio-cesar     20 may 12 01:03  .lesshst
drwxrwxr-x  4 julio-cesar julio-cesar   4096 may  9 19:45  linux
drwxrwxr-x  6 julio-cesar julio-cesar   4096 may 10 15:14  .local
-rw-r--r--  1 julio-cesar julio-cesar     21 jun  1 15:13  .mediainfo-gui
drwxrwxr-x  2 julio-cesar julio-cesar   4096 jun  5 19:00  MKVToolNix
drwxrwxr-x  6 julio-cesar julio-cesar   4096 oct  3  2019  .mozilla
drwxrwxr-x  2 julio-cesar julio-cesar   4096 may  8 19:43  .mplayer
drwxrwxr-x  6 julio-cesar julio-cesar   4096 jun  5 19:02  MystiQ
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may 18  2014  .nero
drwx------  3 julio-cesar julio-cesar   4096 may  9 20:36  .nv
-rw-rw-r--  1 julio-cesar julio-cesar   2470 jun  3 18:46  .nvidia-settings-rc
drwxrwxr-x  2 julio-cesar julio-cesar   4096 may 10 23:16  .oracle_jre_usage
drwx------  3 julio-cesar julio-cesar   4096 may  9 19:13  .pki
-rw-r--r--  1 julio-cesar julio-cesar    807 mar 31 10:41  .profile
drwx------  2 julio-cesar julio-cesar   4096 may 10 16:13  .putty
drwxrwxr-x 15 julio-cesar julio-cesar   4096 sep 13  2023  .q3a
drwxrwxr-x  4 julio-cesar julio-cesar   4096 jun  5 19:05  qBittorrent
drwxrwxr-x  4 julio-cesar julio-cesar   4096 jun  3 14:59  .quake4
drwxr-xr-x  6 julio-cesar julio-cesar   4096 jun  3 13:37  quake4
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may 12 03:38  Scripts
drwxrwxr-x  2 julio-cesar julio-cesar   4096 may 11 02:28 'Shutter Encoder'
drwx------  3 julio-cesar julio-cesar   4096 may 30 22:00  snap
drwxrwxr-x  5 julio-cesar julio-cesar   4096 may 26 23:19  .ssr
-rw-r--r--  1 julio-cesar julio-cesar      0 may  8 17:26  .sudo_as_admin_successful
drwxrwxr-x  6 julio-cesar julio-cesar   4096 jun 13  2023  .thunderbird
drwxrwxr-x  7 julio-cesar julio-cesar   4096 jun  5 13:55  thunderbird
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may  9 19:44  .tor-browser
drwxr-xr-x  3 julio-cesar julio-cesar   4096 may  9 06:24  .var
drwxrwxr-x  7 julio-cesar julio-cesar   4096 may 20 13:08  Ventoy
drwxrwxr-x  3 julio-cesar julio-cesar   4096 may  9 19:44  .waterfox
-rw-rw-r--  1 julio-cesar julio-cesar    221 may 16 17:46  .wget-hsts
drwxrwxr-x  4 julio-cesar julio-cesar   4096 jun  5 19:15  .wine
-rw-------  1 julio-cesar julio-cesar 503113 jun  5 19:14  .xsession-errors
-rw-r--r--  1 julio-cesar julio-cesar    604 may 12 19:48  .xtimidity
julio-cesar@mi-equipo:~$

Greetings...

[Supersayano]

Since the directory did not exist and for you it seems so important that I created it myself. After entering the command:

sudo chown julio-cesar:julio-cesar chrome-sandbox

I then deleted said directory. And I re-entered the command:

ls -la * | grep root

And this is the console output of said command:

julio-cesar@mi-equipo:~$ ls -la * | grep root
julio-cesar@mi-equipo:~$

Finally I restarted, but unfortunately the problem persists.
Greetings...