Borrowing from the ArchWiki[1] I added export QT_QPA_PLATFORMTHEME=gtk2 to .profile

Now the QT apps that I use look way much better

[1] https://wiki.archlinux.org/title/Uniform_look_for_Qt_and_GTK_applications

Did you run updates before running upgrade? Run updates again.
https://devicetests.com/fix-failed-to-load-module-xapp-gtk3-module-error-ubuntu-2004
TC

I did not upgrade, it was a clean install. And yes, everything was updated.

Turns out the command line will no longer update as well.
Welcome to Linux Lite 5.2 rapidrob
 
Friday 15 September 2023, 11:15:55
Memory Usage: 1077/7944MB (13.56%)
Disk Usage: 25/457GB (6%)
Support - https://www.linuxliteos.com/forums/ (Right click, O...

It would have been odd if the command line worked ok.

The version of Linux Lite being used is focal based.  The stacer PPA software does not have a release compatible with focal.  This conflict is causing the update process to error.  The incompatible ...

Those commands are not allowed to run at user level. Prefix them with
sudo and enter your password if asked.

Processor      : Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
Memory      : 16207MB (2842MB used)
Machine Type      : Notebook
Operating System      : Linux Lite 6.4
User Name      : linuxlite1 (linuxlite1)
Date/Time      : qua 13 set 2023 15:59:47
-Display-
Resolution      : 1920x10...

Of course!  I should have known that.  Thanks.

Any update process requires exclusive access to the update resources and will 'lock' them until finished to prevent other update process being started.
In this case 'apt' has locked the update resources and is preventing another update process starting...

===========================
Install Updates Error log
===========================
Install Updates could not fetch the package cache information lists.
Go to https://www.linuxliteos.com/forums/ and paste the log below into a new or existing thread for a...

The version of Linux Lite being used is jammy based.  The stebbins handbrake PPA software does not have a release compatible with jammy. This conflict is causing the update process to error.

The incompatible stebbins software should be removed from the...

Good job.  After checking the new iso, all the extra changes in french are there.