On my SLS I needed to install iptsd separately to make the stylus work. Unfortunately, the stylus input is stretched across both monitors, when an external one is connected. Here's my /etc/libwacom/microsoft-surface-laptop-studio.tablet:
`
[Device]
Name=Microsoft Surface Laptop Studio
ModelName=Surface Laptop Studio
DeviceMatch=any:name:IPTSD Virtual Stylus 045E:0C1B:;any:name:IPTSD Virtual Touchscreen 045E:0C1B:
Class=ISDV4
Width=309
Height=209
IntegratedIn=Display
Styli=0x000b;0x000c
[Features]
Stylus=true
Touch=true
Buttons=0
`