I wish there was a way to put another phone number under Account / Notifications / Shipping and delivery. Without adding somebody to a "household" or installing apps, I just want someone else to know a package was delivered, and it should be brought inside.
A better method that limits exposing information to Amazon is to set up forwarding rules with your email provider or client.
I recommend stop feeding the beast. Have not used Amazon in 10 years and never will. They are so big that they harm the buying power of the consumer and selling power of the producer. Personal knowledge gained while working with them.