2019.2 & 2019.3 scripting API, large parts are missing. e.g. EventSystems & rawImage

Large parts of the scripting API have disappeared from the manual in 2019.2 and still gone in 2019.3
for example, EventSystems are gone from scripting API in 2019.1 they are here

https://docs.unity3d.com/2019.1/Documentation/ScriptReference/EventSystems.IBeginDragHandler.html

Also, RawImage seems to be gone from the scripting API although it is still in the manual portion
file:///Applications/Unity/Hub/Editor/2019.2.0f1/Documentation/en/Manual/script-RawImage.html

I Also searched the unity site at https://docs.unity3d.com/2019.2 in case I just had a corrupted local copy, the Unity hosted docs are missing large parts of the scripting API.

 

The entire UnityEngine.UI section of the scripting reference appears to have been removed. This is probably related to it having been removed from the engine and placed in a package. Though the package's documentation page says to refer to the now missing scripting reference.

 

But how can I use EventSystems to access drag, pointEnter events?

 

Still same problem: I'm a newbie and many tutorials suggest using RawImage. I'm using 2021.3 LTS and it is still available, but I cannot do much if documentation is missing. I'm willing to switch to a more modern alternative, but to do that I would need the RawImage page to tell "this is obsolete: please use BLABLABLA instead".