Lg ultrafine 5k resolution ubuntu/kubuntu dell xps 9570?

Question

I ve read many articles about how to configure lg ultrafine 5k (lg5k from here on) at 5k resolution on ubuntu/kubuntu, but unfortunately it's still not clear for me am I on 5k currently or not. Let me elaborate, that's how lg5k on dell xps 9570 is detected (connected through thunderbolt3):

☺  lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.5 LTS
Release:    18.04
Codename:   bionic
☺  xrandr --query # at 4096x2304
... skipping internal display info
DP-1 connected primary 4096x2304+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160     60.00 + // notice 3840x2160 is considered higher than 4096x2304 - is it 5k resolution?
   4096x2304     60.00* 
   3200x1800     60.00  
   2560x1440     60.00  
   640x480       59.94  
DP-2 connected (normal left inverted right x axis y axis)
   2560x2880     60.00
☺  xrandr --query # at 3840x2160
... skipping internal display info
DP-1 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160     60.00*+
   4096x2304     60.00  
   3200x1800     60.00  
   2560x1440     60.00  
   640x480       59.94  
DP-2 connected (normal left inverted right x axis y axis)
   2560x2880     60.00

5k resolution = 5120 x 2880
So I have two channels, as far as I understood they both should be configured to 2560x1440 and joined as one display. But I don't have that type of resolutions and second channel i.e. DP-2 is somewhat abstract display (ubuntu doesn t recognize it as display). It's hard to tell, for me atleast, what's going on here. Can someone explain this one for me?

Planning to move to kubuntu 20 lts, booted from usb stick, same story there.

Thanks.