Output resolution still not really changed - Android 12 - LG Velvet 5G (LM-G9000UM)

[CyberZooL]

Output resolution still not really changed - Android 12 - LG Velvet 5G (LM-G9000UM)

My LG Velvet 5G can ouput up to 4K resolution but only at 30Hz.
My goal is to use 1080p 60Hz on 4K TV's
I don't own a 4K TV but for my testing I'm trying to use a 720p resolution on my Full HD PC monitor.

The image displayed on on my monitor actually change when I activate 720p in SecondScreen.
My wallpaper is streched differently and I can see that dpi setting has changed.
But when I go in my monitor settings and show display informations it says that the video signal is still 1080p.

To output the video signal of my phone I'm using a Steam Deck Dock and using the HDMI ouput. Not the DisplayPort ouput.

I used the adb method on my Linux PC to grant SecondScreen system permissions acces.
adb shell pm grant com.farmerbb.secondscreen.free android.permission.WRITE_SECURE_SETTINGS

I have tried a couple of settings in SecondScreen and I was not successful to obtain a true 720p resolution on my setup. That means that it would not work on a 4K TV too.

If there is a solution to this problem that would be very nice.

[samuelzamvil]

Same issue on Android 14 with a Google Pixel 8 Pro. Resolution of the internal display changes but output resolution via DP Alt Mode using HDMI remains the same.