I am in Edit mode and face selection is activated, however no face has a black dot in the middle.
How can I display the face center in Blender 4?
It's not here by default anymore but you can activate their visibility in the Mesh Edit Mode Overlays panel > Center. Note that you need to be in Face select mode to see them :
The dots only appear in X-Ray mode while in Edit mode, which you can enable with Alt+Z.
You can also enable Normals, under Mesh Edit Overlays. (In the top-right, just to the left of X-Ray and the toggles for Viewport shading)
That allows you to always see the direction, and effectively the center, of all faces.
If you don't like the little blue lines sticking out of everything, you can turn down the size to shorten them.