UE4 viewport not working (4-21)

Hi,
I work on a Linux system(Ubuntu 20.0), and recently built UE4 from source. When I open a project, the viewport looks like a blank flashing screen that changes colours when I navigate around it. It changes from a dark blue to a peach colour, and I can’t see any of the objects in the scene.
Would really appreciate any information related to this.

Thanks!