Increasing screen resolution in X11 and solving it with xrandr

I am using X11 on Ubuntu 22.04

I am trying to configure my big flatscreen as a monitor, connected by a HDMI cable. The picture is very inaccurate. Unfortunately I only get a resolution of 1920x1080. I did the following to increase the resolution:

abc@abc:~$ xrandr --listactivemonitors
Monitors: 2
   0: +*DP-9 1920/527x1080/296+1920+0  DP-9
   1: +HDMI-3 1920/1218x1080/685+0+0  HDMI-3
abc@bc~$ cvt 3840 2160
# 3840x2160 59.98 Hz (CVT 8.29M9) hsync: 134.18 kHz; pclk: 712.75 MHz
Modeline "3840x2160_60.00"  712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
abc@abc:~$ xrandr --newmode "3840x2160_60.00"  712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
abc@abc:~$ xrandr --output HDMI-3 --mode "3840x2160_60.00"
xrandr: cannot find mode 3840x2160_60.00

Why doesn't this work?

Let me add the following:

abc@abc:~$ inxi -G 
Graphics:
  Device-1: NVIDIA TU102 [GeForce RTX 2080 Ti Rev. A] driver: nouveau
    v: kernel
  Device-2: NVIDIA TU102 [GeForce RTX 2080 Ti Rev. A] driver: nouveau
    v: kernel
  Device-3: NVIDIA TU102 [GeForce RTX 2080 Ti Rev. A] driver: nouveau
    v: kernel
  Display: x11 server: X.Org v: 1.21.1.3 driver: X: loaded: modesetting
    unloaded: fbdev,vesa gpu: nouveau resolution: 1: 1920x1080~60Hz
    2: 1920x1080~60Hz
  OpenGL: renderer: NV162 v: 4.3 Mesa 22.2.5

Tried not specifying the rate or setting it with the --rate option which is what should be used for setting the refresh rate? Ie:

xrandr --output HDMI-3 --mode 3840x2160 --rate 60