In these modern, commercially-driven times, Ducati solus dealers, (who are Ducati trained and indoctrinated) will only want to use Ducati OEM parts for any work that they do. This extends to belts and other items that you can get from other sources. Sometimes they will cite "warranty issues", but usually it's about using parts where Ducati make the profits.
Tyre inner tubes are made by the same people that make tyres (usually) and you can by normal ones, or heavy duty, and like many products, you get what you pay for (so don't buy cheap crap), but any non affiliated tyres shop would just use a quality inner tube from any reputable manufacturer. If Ducati do actually have an official inner tube (which would surprise me) then someone else makes it for them, and it's not in any way special or unique. In fact it's likely to be sourced according to price and not quality.
If you want a qualified opinion (after all, I'm just a blogger and a biker) then please don't take my word for it, and ring a Pirelli dealer and ask what tubes they would recommend and supply for your bike, as it's their product that you are using.
As for lightweight, vs normal vs heavy duty... Well, lightweight ones save weight... but may puncture more easily, normal ones are just normal, and heavy duty ones are favoured by offroad riders, and they do last longer, but they also weigh more - which is may not be what you want on your un-sprung rotating mass. (...in my unqualified opinion)
...any inner tube is fine. Take the bike to a tyre shop, not a Ducati dealer, or just get your mech to order whatever inner tube he would fit to any rims of that size.
