are there any sonatas with actual fingering
and when the diamonds and circles switch staves is that a crossing of hands or a changing of voice
The original manuscripts provide no fingering at all.
In some of the sonatas the hand crossing is indicated, but that does not mean that you are not to use hand crossings if not indicated.
The Longo edition has fingerings, but mostly they are not really appropriate to the style.
Some editions have excellent fingerings, but they only have a limited number of sonatas. For a discussion of these editions have a look here:
https://www.pianostreet.com/smf/index.php/topic,10649.0.html(Discussion on some of Scarlatti editions)
I assume you are talking about the Sankey edition that has the first 127 sonatas available for free on the net. If so, diamond shaped heads are to be played with the left hand and round headed notes are to be played with the right hand. However keep in mind, that this is Sankey’s (informed) opinion. We do not really know if that is how Scarlatti played them.
Read Sankey’s notes on his edition here:
https://www.sankey.ws/(Sankey’s site)
Best wishes,
Bernhard.