shaders – Updated Unity project from 2020.2.1f to 2021.1.7: lighting is messed up, scenes are brighter

I’ve updated my project from 2020.2.1f to 2021.1.7 (also tried 2020.3.8), and now my scenes are much brighter for some reason:
enter image description here

Any tips?

Current I use the standard pipeline I think, because the Render Pipeline Asset is set as None.

I have only one realtime directional light in the scene, and no Lighting Settings set in the Lighting window. The environment is the Default-Skybox.