About the broken UI in Light mode (Preferences > General > Editor Theme > Light), this is a known issue the UIToolkit team is looking at right now. In my case, toggle Dark back to Light solved the issue but it might depend on the build version you are on.
Great, thanks.
And about the slow refresh & slow search?
Hi there, we are aware of and we are in the progress of trying to fix some performance issues with the Package Manager window.
However, we are not sure if the things are are trying to fix are exactly the same as the issues you are talking about. If you would like to make sure that the exact issues you are experiencing is brought to our attention and speed up the fixing process, please feel free to submit a bug with us
With detailed bug report, it’s more likely that we can ping point and fix issues faster.
Best