Check the screen before the filter
Frame the camera so the screen covers the background area you intend to remove. Inspect the image for shadows and uneven colour before adjusting the filter. Change the light or screen position and compare the picture.
Plan the camera and your face light together with the streaming lighting layout. These are setup checks, not a claim that a particular screen guarantees a clean edge.
Add Chroma Key to the camera source
In OBS, open the camera source’s Filters and add Chroma Key as an effect filter. Choose the screen colour. Adjust Similarity to cover the colour range, then Smoothness and Key Color Spill Reduction while checking the subject’s edge.
Do not keep increasing the range if it removes parts of your clothing or face. Compare the unfiltered source and repair the background image first. The filter removes matching colour; it cannot know which green object belongs in the scene.
Record movement and scene changes
Record your normal movements, hair edges and objects you hold. Switch to the scenes you will use and check that the key stays on the intended source. Keep a fallback scene for a failed camera or lighting change.