Already tried many soultions from the internet, but no one of them worked.
I suspect it’s b/c the Point Light 2D is under the Canvas. I don’t think this feature was developed with UI in mind. Also it has a huge z-value, not sure what that’s going to do. Finally, 2020.2 might be lacking bug fixes of the 2020.3 LTS though for the previous reasons I’d be a bit doubtful that would fix it.
You might be able to accomplish something similar with a semi-transparent sprite instead. That would play well with the Canvas / UI.