GNOME 50 with fully supported fractional scaling was released in the repos, so I tried it out, scale = 125% has the same issue. However, Large Text seems to be unaffected now.
Updated Steam version: 1775605734
Updated GPU driver: nvidia-open 595.58.03-3 (old was 595.58.03-1)
Steam Version: 1785187029
Opted into Steam client beta?: no
Have you checked for system updates?: yes
Operating System: Kubuntu 26.04 LTS
KDE Plasma Version: 6.6.5
Kernel Version: 7.0.0-28-generic (64-bit)
Graphics Platform: Wayland
Graphics Processor 1: AMD Radeon RX 7800 XT
I have the same issue with the mouse cursor being displaced when using scaling (140% in my case.) Problem goes away when scaling is set to 100%.
Nothing extracted yet.
System information
Description
On my system if I enable display scaling 125% in KDE or the "large text" accessibility option in GNOME (which seems to apply the same scaling factor), then when using Steam Link for Android and enabling the Direct Cursor mouse mode, the place I tap on the phone is not the place the mouse cursor actually clicks. Moving the mouse around, the cursor appears in different places on each device. If I use the trackpad mode in the Android client, there is no issue.
I tested with various games on Proton (initially Proton-GE, then Proton 10) and all had the same result. The Steam UI itself also has the issue.
Using the "Scaled by the system" option in KDE for X11 app scaling makes the issue go away, but this results in blurry applications.
In the Android app settings, I tried automatic resolution and resolution limited to 2560x1440 and saw no difference.
Here is a comparison where I moved my mouse so it was at the bottom right corner on my desktop, the second screenshot is where it appeared on my phone, next to "INPUTS":
My display settings: