When a Wacom Tablet is plugged into a Linux Computer with multiple screens, it is being mapped to all of them which makes it hard to write. Here is how to map it to one particular screen:

BUT: This way works only for Xorg. If you are running Wayland, you can configure these settings with "libinput". Some Desktop Environments even have a GUI program in their Wayland version specifically made to handle the libinput settings for you! GNOME has full support for configuring buttons and mapping the tablet to a monitor. KDE Plasma also has full support for configuring buttons and mapping the tablet to a monitor. You can read more about this here.

$ xinput

The output should look somewhat like this:

[user@host ~]$ xinput
⎡ Virtual core pointer                    	id=2	[master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer              	id=4	[slave  pointer  (2)]
⎜   ↳ bcm5974                                 	id=12	[slave  pointer  (2)]
⎜   ↳ SINO WEALTH Thunderobot KG3089 Consumer Control	id=13	[slave  pointer  (2)]
⎜   ↳ SINO WEALTH Thunderobot KG3089 Mouse    	id=18	[slave  pointer  (2)]
⎜   ↳ Logitech G305                           	id=19	[slave  pointer  (2)]
⎜   ↳ Wacom One by Wacom S Pen Pen (0)        	id=22	[slave  pointer  (2)]
⎣ Virtual core keyboard                   	id=3	[master keyboard (2)]
    ↳ Virtual core XTEST keyboard             	id=5	[slave  keyboard (3)]
    ↳ Power Button                            	id=6	[slave  keyboard (3)]
    ↳ Video Bus                               	id=7	[slave  keyboard (3)]
    ↳ Power Button                            	id=8	[slave  keyboard (3)]
    ↳ Lid Switch                              	id=9	[slave  keyboard (3)]
    ↳ Sleep Button                            	id=10	[slave  keyboard (3)]
    ↳ Apple Inc. Apple Internal Keyboard / Trackpad	id=11	[slave  keyboard (3)]
    ↳ SINO WEALTH Thunderobot KG3089 Consumer Control	id=14	[slave  keyboard (3)]
    ↳ SINO WEALTH Thunderobot KG3089 Keyboard 	id=15	[slave  keyboard (3)]
    ↳ SINO WEALTH Thunderobot KG3089 System Control	id=16	[slave  keyboard (3)]
    ↳ SINO WEALTH Thunderobot KG3089          	id=17	[slave  keyboard (3)]
    ↳ Logitech G305                           	id=20	[slave  keyboard (3)]
    ↳ Wacom One by Wacom                       	id=21	[slave  keyboard (3)]

We can see that in this case, the Wacom Tablet has the ID "21", and the pen of the tablet has the ID "22".

The next thing we want to do is finding out the name of the screen we want the tablet to be mapped to. We can do that by executing:

$ xrandr

The output should look somewhat like this:

[user@host ~]$ xrandr
Screen 0: minimum 320 x 200, current 3360 x 1080, maximum 16384 x 16384
eDP-1 connected 1440x900+1920+0 (normal left inverted right x axis y axis) 286mm x 179mm
  1440x900      59.84*+
  1400x900      59.96    59.88
  1440x810      60.00    59.97
  ...
HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm
  1920x1080     60.00*+  50.00    59.94
  1680x1050     59.88
  1600x900      60.00
  ...

We now see all of our screens connected to the computer. We can also see our primary monitor which we want the tablet to be mapped to:

HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm

Now we have all information needed to map the Wacom tablet to our primary screen only. Let's do it:

$ xinput map-to-output "penID" "name-of-screen"

For my example the command would look like this:

$ xinput map-to-output 22 HDMI-1

Congratulations! You now mapped your Wacom Tablet to one specific monitor! Happy writing, happy drawing!