using 2 displays 1 high resolution

I am using KDE Plasma on Tumbleweed with the latest update…

I don’t know if it’s possible to do what I want to do… So my laptop has super high resolution, 3480x2160. In order to make all the fonts readable at this highest resolution, I messed around with it and finally found settings that work for me under system settings: All fonts set at 14pt, Force font DPI to 192, and the Global Scaling value is set to 150%.

The challenge is my laptop screen is only 13 inches, so even though my screen is readable, I still would like to set up a 2nd display that is at least 21 inches that I can plug into my laptop and use with a side by side configuration. But it makes things a real challenge. The extra display I have has a max resolution of 1920x1080. So when I connect the hdmi to my external display, everything is huge because of the global scaling, big font, and high font DPI setting.

If I set the resolution lower on my laptop, that works ok for both, but it seems like there is something missing in reading the laptop display. I might be able to figure out how to live with it, but I am hoping to be able to fully utilize the high native resolution instead of downgrading it.

So I am wondering if there is a way to set the global scaling value and font DPI values to something different for the different displays? It seems like if I could do that, then I could make these 2 displays work together.

I have an ASUS Zenbook flip s ux-371 laptop.

This is my hardware for the graphics card:

> /usr/sbin/hwinfo --gfxcard
24: PCI 02.0: 0300 VGA compatible controller (VGA)               
  [Created at pci.386]
  Unique ID: _Znp.1zXojHeem29
  SysFS ID: /devices/pci0000:00/0000:00:02.0
  SysFS BusID: 0000:00:02.0
  Hardware Class: graphics card
  Device Name: "VGA"
  Model: "Intel TigerLake-LP GT2 [Iris Xe Graphics]"
  Vendor: pci 0x8086 "Intel Corporation"
  Device: pci 0x9a49 "TigerLake-LP GT2 [Iris Xe Graphics]"
  SubVendor: pci 0x1043 "ASUSTeK Computer Inc."
  SubDevice: pci 0x1362  
  Revision: 0x01
  Driver: "i915"
  Driver Modules: "i915"
  Memory Range: 0x603e000000-0x603effffff (rw,non-prefetchable)
  Memory Range: 0x4000000000-0x400fffffff (ro,non-prefetchable)
  I/O Ports: 0x3000-0x303f (rw)
  Memory Range: 0x000c0000-0x000dffff (rw,non-prefetchable,disabled)
  IRQ: 157 (106861 events)
  Module Alias: "pci:v00008086d00009A49sv00001043sd00001362bc03sc00i00"
  Driver Info #0:
    Driver Status: i915 is active
    Driver Activation Cmd: "modprobe i915"
  Config Status: cfg=new, avail=yes, need=no, active=unknown


Not sure, but this may help:
see https://forums.opensuse.org/showthread.php/540391-X11-KDE-multiple-monitors-with-different-resolutions?p=2937891#post2937891 and also the linked post.

https://wiki.archlinux.org/title/HiDPI
https://duckduckgo.com/?q=kde+hidpi