Download qres.exe and on sunshine browser tab -> Applications under Command Preparations insert this strings:

Do Command:

C:\qres\QRes.exe /x:1280 /y:800

Undo Command:

C:\qres\QRes.exe /x:1920 /y:1080

C:\qres is path. Sorry for my english.

Hi thanks for the answer, I saw some posts about what you mentioned but didn't manage to make it work.

In the end I solved with this https://github.com/Nonary/ResolutionAutomation/releases/tag/2.0.15_gfe a script to automatically change resolutions using moonlight directly though nvidia geforce experience. It works very well and it easy to install.

I took all today between this and solving the stutterings (very tricky , with lots of different possible solutions) but now I think i got quite satisfied with the experience :)

BTW your english is fine! also in my case it is my second language

I run .sh on boot in /home/.Shellscripts/Steamdeck/Configs/Display. I have HDMI dummy plug and stream my desktop from sunshine.

#!/bin/sh
#set ress 1440p120
sleep 3
xrandr --newmode 2560x1440R  497.25  2560 2608 2640 2720  1440 1443 1448 1525 +hsync -vsync
sleep 3
xrandr --addmode DisplayPort-0 2560x1440R
sleep 3
xrandr --output DisplayPort-0 --crtc 0 --mode 2560x1440R

I also have desktop icon that make default boot session gamescope/kde desktop mode

#!/usr/bin/env xdg-open
[Desktop Entry]
Comment=Boots to Gamescope every time
Name=Always Boot to Gamescope
Exec=steamos-session-select gamescope
Icon=steamdeck-gaming-return
Terminal=false
Type=Application
StartupNotify=false

[Desktop Entry]
Comment=Boots to Desktop every time
Exec=steamos-session-select plasma-x11-persistent
Icon=steamdeck-gaming-return
Name=Always Boot to Desktop
StartupNotify=false
Terminal=false
TerminalOptions=
Type=Application

in shunshine I call steamos-session-select <session name> it switches session when it's booted. sometimes hangs but restart fixes it. After reboot switching to other session works 100% but do it 6 times and it will crash.