no icons in download dialog window in Lubuntu 22.04 LTS

[paulduif]

Recently I installed Lubuntu 22.04 LTS to find out that whenever I download something, like in the attached example picture, the icons are missing from the resulting dialog box.

Also I noticed the very spartan look of this box which cannot be resized to have a smaller width than you can see in this picture.

I verified if this was the result from a fault on my installation by running the 'live'-cd (usb-stick) and it reproduced ! So it must be something in Lubuntu itself or some conflicting issue with my laptops hardware?

btw: the same happens with the upload dialog box.

I have these questions:
1) are these dialog boxes the correct ones or has something to be changed in my setup?
2) is there any way to tune the appearance of these boxes?
3) is it possible to install something to have more 'normal' boxes for these dialogs?

Any help is very much appreciated.

Paul