Solved:

The dev updated the theme (I am using Kripton https://github.com/EliverLara/Kripton)

So I want to get rid of these grey boxes that got added to everything in the overview. They are in the bar as shown in the image, they are in every text in the overview search as well.

For my taste it is disgustingly ugly. And I can't find where I can make it go back to normal.