So I successfully added paddle shifters to a 17 Giulia that came without them. I cannot speak for 18+ models as they have the security gateway feature that does not allow access to the ECU.
First off the tools you will need will be a smaller 1/4 ratchet, an extension, a t20 bit and a t8 Allen style key, that's it.
Now for the first step remove the negative wire from the battery terminal and let it power down for about 5 mins.
***Do not attempt to unlug the connections with out powering down the car, by disconnecting the battery. I am not sure what will happen but I would rather not get an airbag to the face. ****
After doing so remove the two screws underneath the cowl that hold it up with the t20 bit and ratchet with extension. I bought a complete cowl off of eBay for 80 dollars, that came out of a 18 stelvio. It fits perfectly with no fitment issues. You can see from the picture the stelvio cowl on the left and the Giulia on the right. The dealer wants 50 for the bottom piece and 140 for the top piece, so I opted to buy used off eBay.
Once removed you will see 3 wires hooked up and aurther down the harness some brown tape with a connection taped off, that is for the paddle shifters. Remove the brown tape and disconnect the 3 hook ups.
Now the paddle shifter I ordered from eBay came off of a 18 Giulia and came with the switch assembly. You only need the paddle shifters themselves. So I removed the screws (keep them) and the paddle shifters them selves. The dealer said these can be ordered for 360. I have seen them as low as 125 on eBay. But be careful as they look rough and broken where the screws go. Mine however where in top notch used condition.
Once you have taken them apart you will hook them up to your car the same way you took them off the other assembly. Use the t8 Allen key on the 4 screws. Once put on, hook all of the connections back up, plugging in the taped off
connection to the paddle shifters.
Last step is putting the bottom piece of the cowl back on. And hook the negative battery terminal back up. You will have errors on the dashboard due to disconnecting the battery. So you won't have any of the nannies such as traction control for a bit. All these will go off after you drive it for a bit.
For the programming I used a registered copy of multiecuscan 4.3 paired with,
Granted you do not need all the adapters, however you do need the blue and grey to finish the proxi alignment.
From within multiecuscan choose the Giulia 2.0 turbo 16v multiair, then choose body, then choose CAN setup / PROXI alignment procedure (952).
From within the next menu choose at the top "adjustments" look for the paddle shifters adjust it to "present" and then the last step is run the proximity alignment, that is the first option on that page. Follow the on screen prompts and you'll then have paddle shifters.
Hopefully this helps someone. I take no responsibility if you screw up your car in doing this. This is just my experience in doing it in my car. Feel free to ask questions.