VLC and other apps not opening. How do I fix this issue? Ubuntu 20.04 still not solved

So a couple years ago, I noticed that VLC stopped opening. I later found this true for a range of other applications I'd downloaded previously - Calibre, E- book viewer, E-book editor, Deep in Voice Recorder, LRF viewer, Simple Screen Recorder, Kleopatra, and SM Player.

I'm working with Ubuntu 20.04, updated at some stage from 20.02

These are the steps I've taken so far -

-I've uninstalled and reinstalled VLC (the most important one for me) from the terminal to no avail,

-I've had the problem diagnosed as being "skins2 interface error: cannot instantiate dialogs provider"

• on typing vlc, this comes up -

jack@jack-HP-ZBook-17:~$ vlc
VLC media player 3.0.9.2 Vetinari (revision 3.0.9.2-0-gd4c1aefe4d)
[000055d7436145b0] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[000055d7436f64b0] skins2 interface error: cannot instantiate dialogs provider
[000055d7436a77d0] main playlist: playlist is empty
[000055d7436f64b0] [cli] lua interface: Listening on host "*console".
VLC media player 3.0.9.2 Vetinari
Command Line Interface initialized. Type `help' for help.
> 

• I tried this instruction from @Raffa
• sudo apt install --reinstall vlc vlc-plugin-qt vlc-plugin-skins2
  and this didn't work -

jack@jack-HP-ZBook-17:~$ sudo apt install --reinstall vlc vlc-plugin-qt vlc-plugin-skins2
[sudo] password for jack: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-hwe-5.15-headers-5.15.0-48 linux-image-5.15.0-48-generic
  linux-modules-5.15.0-48-generic linux-modules-extra-5.15.0-48-generic
Use 'sudo apt autoremove' to remove them.
0 to upgrade, 0 to newly install, 3 to reinstall, 0 to remove and 230 not to upgrade.
Need to get 1,560 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://hk.mirrors.thegigabit.com/ubuntu focal/universe amd64 vlc amd64 3.0.9.2-1 [34.0 kB]
Get:2 http://hk.mirrors.thegigabit.com/ubuntu focal/universe amd64 vlc-plugin-qt amd64 3.0.9.2-1 [1,054 kB]
Get:3 http://hk.mirrors.thegigabit.com/ubuntu focal/universe amd64 vlc-plugin-skins2 amd64 3.0.9.2-1 [471 kB]
Fetched 1,560 kB in 9s (170 kB/s)                                              
(Reading database ... 255552 files and directories currently installed.)
Preparing to unpack .../vlc_3.0.9.2-1_amd64.deb ...
Unpacking vlc (3.0.9.2-1) over (3.0.9.2-1) ...
Preparing to unpack .../vlc-plugin-qt_3.0.9.2-1_amd64.deb ...
Unpacking vlc-plugin-qt:amd64 (3.0.9.2-1) over (3.0.9.2-1) ...
Preparing to unpack .../vlc-plugin-skins2_3.0.9.2-1_amd64.deb ...
Unpacking vlc-plugin-skins2:amd64 (3.0.9.2-1) over (3.0.9.2-1) ...
Setting up vlc-plugin-qt:amd64 (3.0.9.2-1) ...
Setting up vlc (3.0.9.2-1) ...
Setting up vlc-plugin-skins2:amd64 (3.0.9.2-1) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for libvlc-bin:amd64 (3.0.9.2-1) ...
Processing triggers for desktop-file-utils (0.24-1ubuntu3) ...
Processing triggers for mime-support (3.64ubuntu1) ...
Processing triggers for gnome-menus (3.36.0-1ubuntu1) ...
jack@jack-HP-ZBook-17:~$ vlc
VLC media player 3.0.9.2 Vetinari (revision 3.0.9.2-0-gd4c1aefe4d)
[000055981ced35b0] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[000055981cfb45c0] skins2 interface error: cannot instantiate dialogs provider
[000055981cf667d0] main playlist: playlist is empty
[000055981cfb45c0] [cli] lua interface: Listening on host "*console".
VLC media player 3.0.9.2 Vetinari
Command Line Interface initialized. Type `help' for help.
> 

-I tried vlc --intf qt a suggestion from @Archisman Panigrahi also did not work. Here's what happened -

jack@jack-HP-ZBook-17:~$ vlc --intf qt
VLC media player 3.0.9.2 Vetinari (revision 3.0.9.2-0-gd4c1aefe4d)
[000055e96026f110] main interface error: no suitable interface module
[000055e96018e5b0] main libvlc error: interface "default" initialization failed
jack@jack-HP-ZBook-17:~$ 

-Following advice from @RonJohn, and this link - VLC media player not working: No Interface I followed a similiar protocol to the one from the link, yet the end result was pretty much the same... HOWEVER I FEEL THIS IS CLOSE???

ack@jack-HP-ZBook-17:~$ vlc -v
VLC media player 3.0.9.2 Vetinari (revision 3.0.9.2-0-gd4c1aefe4d)
[0000555756a2d5b0] main libvlc warning: cannot load module `/usr/lib/x86_64-linux-gnu/vlc/plugins/gui/libqt_plugin.so' (/usr/lib/x86_64-linux-gnu/vlc/plugins/gui/libqt_plugin.so: undefined symbol: _ZN17QAbstractItemView11eventFilterEP7QObjectP6QEvent, version Qt_5)
[0000555756a2d5b0] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[0000555756b0e740] skins2 interface error: cannot instantiate dialogs provider
[0000555756ac08a0] main playlist: playlist is empty
[0000555756b0e740] [cli] lua interface: Listening on host "*console".
VLC media player 3.0.9.2 Vetinari
Command Line Interface initialized. Type `help' for help.
> shutdown vlc
Shutting down.
[0000555756b0e740] [cli] lua interface: Requested shutdown.
jack@jack-HP-ZBook-17:~$ dpkg -S libqt_plugin.so
vlc-plugin-qt:amd64: /usr/lib/x86_64-linux-gnu/vlc/plugins/gui/libqt_plugin.so
jack@jack-HP-ZBook-17:~$ ls -l /usr/lib/x86_64-linux-gnu/vlc/plugins/gui/libqt_plugin.so
-rw-r--r-- 1 root root 3508520 Apr 10  2020 /usr/lib/x86_64-linux-gnu/vlc/plugins/gui/libqt_plugin.so
jack@jack-HP-ZBook-17:~$ sudo apt istall -- reinstall libqt_plugin.so
[sudo] password for jack: 
E: Invalid operation istall
jack@jack-HP-ZBook-17:~$ sudo apt install --reinstall libqt_plugin.so
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package libqt_plugin.so
jack@jack-HP-ZBook-17:~$ 

What am I doing wrong here??

I'm an ABSOLUTE NOOB when it comes to coding, computers and running commands through the terminal. I'm at the ABSOLUTE BEGINNER LEVEL - so assume I know nothing.

Haven't looked much into the other apps that aren't working - I've just found workarounds, and alternative softwares that do seem to work.

Any more help to finally fix this would be great.

Thanks

I've uninstalled and reinstalled VLC (the most important one for me) from the terminal to no avail,

VLC seems to be currently installed on your system.

When I type "vlc media player" into the terminal, it comes up with this -

Just vlc is the command ... media player are seen as arguments i.e. media files to open hence the errors you see:

filesystem stream error: cannot open file /home/jack/media (No such file or directory)

filesystem stream error: cannot open file /home/jack/player (No such file or directory)

Then the cursor keeps hanging there, as if waiting for another command.

No, it's not waiting for another command ... It's waiting for the current command i.e. vlc to finish i.e. until the GUI is closed/terminated.

If you want to use the terminal after launching VLC and keep VLC running at the same time, then send it to the background like so:

vlc &

And if you want VLC to keep running even after closing its parent terminal(the one you just launched it from), then send it to the background and detach it from the parent terminal like so:

vlc & disown

That said, it appears that either a VLC GUI dependency is missing and in this case reinstalling VLC with it's key GUI packages might be required like so:

sudo apt install --reinstall vlc vlc-plugin-qt vlc-plugin-skins2

Or if that is not the case, then make sure that you are not logged in via terminal and no display server session is available.