There are so many "solutions" to package thievery, it is almost bewildering. Amazon will sell you a door lock that they can open to put your package inside. Of course, if you have an alarm system, that won't work. If you leave a car parked outside, Amazon will put your package in the trunk (As if car break-ins weren't common enough already. Our neighbor is a police sergeant. His family's cars are NEVER left outside. Neither are ours.) If you have certain web-enabled garage door openers, you can arrange for Amazon to put your package in the garage. Of course they can also deliver to a designated Amazon lock box at a convenience store or gas station. Or you can pick up your package at a UPS store. For a while, we tried having deliveries to my wife's office, but the building is locked after 6pm and on weekends--and the "no weekend delivery" option, if it is still offered, doesn't work anyway. Amazon uses FedEx, UPS, USPS, and a UPS-USPS combo service. They also use their own trucks when they have warehouses in your area, as well as contract delivery trucks and even a package delivery equivalent of Uber. The Amazon and local delivery people usually take a picture of the package next to your door and text it to you as proof of delivery.
Having your packages signed for, is not always available and not always a good idea. If you're not there to sign twice, then you have to go to the UPS warehouse (in a scary part of town and with limited hours) to get it. With Amazon, you can specify "Please ring doorbell" and most of the time that will tell you your package is there, if you are there when it's delivered. Not always, though, as it takes one or two seconds to push a doorbell button. Often, I find out a package is at my front door when I get a text message on my phone. Yes, the delivery guy had time to take a picture with his phone but not press the doorbell.
Door bell cameras like Ring (owned by Amazon) or Blink (also owned by Amazon) are of fairly little real value in catching a thief, although they might be useful as proof, if the thief happens to be caught. Here in the greater Houston area, you can take your video to the police and learn that there are 60 others from today ahead of you, just in your area. You can get a big ugly box with a bar code scanner for UPS to have your package scanned to open the box which will not open again except with your key. You can also get a box and have an open padlock with a note for UPS to lock after putting your package inside. Of course these depend on the delivery guy paying attention to your note and that your package will fit in the box and that the box itself cannot be easily taken.
I remember a youtube video of a guy who booby trapped a box with some kind of firecracker after repeated thefts by the same guy (he had a Ring camera so he knew it was the same guy.) That's generally not a good idea. Booby traps almost always end up with the trapper getting arrested, sued, or both. If you don't have Amazon local delivery where you can see where the truck is, the only sure way is to, on delivery days, sit in a rocking chair on your front porch and wait. Be sure to put the chair(s) away afterward (the chairs on our front porch were stolen!)