I post below a link towards a wonderful article on La Vecchia Signora (on Kapherus'blog about the Vera Sibilla Italiana).
https://sibillareadings.wordpress.com/2019/07/27/musings-on-la-vecchia-signora-the-old-lady/
I post the link here in the Oracle section because the section with regard to Cartomancy doesn't include the Sibilla but it would be more its "natural place" somehow.
The article really goes in depth and gives a practical example too. Otherwise we always learn something interesting, here that the Sibilla was derived and expanded from the Austrian Gypsy Cards (Zigeunerkarten), actually it's something I didn't know at all while I noted a few similarities between the cards for these decks.
Well, I'm a fan!
For this little deck I don't know other very good online resources currently, while maybe in the past there were some great resources on the internet, but websites disappear at times. Otherwise and to be fair I think that there are certainly wonderful resources in Italian language, but I don't understand Italian at all so I'm pretty limited here!