This is fairly complicated to do locally and securely. If any e-commerce website/app could add tracking numbers as PINs to your smart lock via the local network, that would be a security nightmare. You'd also have to provision domains for every smart lock so that every lock can get Let's Encrypt certs and accept requests from web browsers without configuration. Not to mention most tracking numbers are easily guessable because they consist of a destination code and an auto-increment integer.

Also a lot of companies don't assign a tracking number until the package gets transferred to the last mile carrier. Again, if you're willing to manually copy-paste the tracking number after you get the shipping notification every single time you order something, you're clearly not part of the target demographic