Symptoms

The remote session is blurry on screens with 4K and higher resolution and scaling of over 150%.

Cause

Below listed Group Policies are responsible.

Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Remote Session Environment:

RDP:

Set compression algorithm for RDP data

Optimize visual experience for Remote Desktop Server Sessions

RemoteFX:

Configure RemoteFX Adaptive Graphics

Configure compression for RemoteFX data

Configure image quality for RemoteFX Adaptive Graphics

Optimize visual experience when using RemoteFX

Resolution