Please allow all I mean all iPads connect to a Apple Pencil

Here is Apple’s definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

Older models of iPad that are not listed lack the specific screen hardware with which the Apple Pencil interacts with compatible models of iPad. As compatibility is dependent upon hardware, you simply cannot enable compatibility by a way of a software update.

NO Pencils will work with any old/er 6-10-year old iPad models, as well as the 2017, iPad 5th generation.

These old/er iPad models lack the crucial and necessary internal screen hardware layer needed for an Pencil to be recognised by an iPad's screen and to properly function/interact with an iPad’s screen.

Some older iPads cannot make that connection because they lack the components necessary for that function.