Arrow down -> Menu -> General settings -> Activate installation of HDF default picons = "Yes"
reboot

And have a look at this link:
Wechsel VU+ Duo2 -> UE 4k Cable - LCD anpassen

Set:
Arrow down -> Menu -> General settings -> Show Picons in Channellist = "Yes"
reboot

Do picons show up thereafter in channellist ?

Please give us the result of:

grep -i piconsPath /etc/enigma2/settings

Please logon to your box as user root per OpenWebInterface or SSH.

OpenWebInterface:
Enter the IP-Adress of your box in the Adressfield of your Browser (Firefox, Chrome, Edge, ...)
In the navigation field on the left of the OpenWebInterface click on Terminal.
Now logon as user root and the associated password.
Now run on the command line:
grep -i piconsPath /etc/enigma2/settings

Please post the result here.


SSH:
SSH is a little program to log in to remote machines. If you don't have it, you can download it from:
chiark.greenend.org.uk/~sgtatham/putty/latest.html

Install it, start it, enter the IP-Adress of your box, logon as root, ... the rest is the same as above.

Please post the result of the command:

grep -i piconsPath /etc/enigma2/settings

here.

It will probably only be a few lines.

My LCD-Picons are in usr/share/enigma2/piconlcd. And they appear on the display.

Yes, this is the correct path to the sender picons.
The directory /usr/share/enigma2/picon should now be full of sender picons
and with skin_display_picon_11 you should see the corresponding sender picon
at every sender change on the LCD display.

Does it work now in principle, or not ?
If yes, then get you the needed picons and put them in /usr/share/enigma2/picon

What image other than OpenHDF ?

You have now the all the knowledge you need to get picons to work on the LCD display of the Quad 4K.
In principle all the images under the hood of the Open Enigma Alliance are very similar to each other.