USPS Leaves Packages @ Garage Door

Just be polite and friendly if you discuss the matter with the substitute carrier. Actually you are fortunate that you have ONLY one substitute. Many post offices shuffle the subs from route to route filling in for the regular carrier or to reduce overtime costs. Remember Newman on the Seinfeld TV show. Some USPS employees can be nasty and do delivery things just out of spite. I knew a letter carrier in PA who told stories about how he would FEED the mail to angry dogs who attacked the mail slot in the owner's front door on every mail delivery. Nothing like receiving shredded mail or damaged packages.
I've thought about going out to speak with him, but I'm a 6', 220# guy... I don't think I'm intimidating, but my I've been told I am by others; my SIL recently described me as scary. lol

I feel your pain. I apparently intimidate people every day of my life but I never ever intend to. I am big and muscular but I have a gentle voice. I dress fairly well and I am well groomed and no tats or anything, so I do not understand why some are scared of me. Its totally unecessary.
Schools and some folks have been brainwashed about this thing called "toxic masculinity" it's a really messed up line of thinking, pretty much on purpose...............but that drifts us into untouchable subjectz

BACK on topic. Yes LAZY delivery services. UPS is the WORST.

Last year - with three other logical package delivery drop locations around my house and shop, UPS driver chose the LMD. (Lazy Man Decision) SOB just wheel them straight up and left a pile in the most visible location. I am darn lucky I got home right after because we have had packages stolen! I griped and sent the pic to UPS, has not happened since.

I had a package ship from King of Prussia. 2 weeks after I got it, tracking still showed it had been picked up at KoP, nothing else.
I can confidently say that that isn't normal. The fact that NO tracking details occured after the initial pick-up scan was done clearly shows something wasn't right.
The Fedex and UPS apps, along with the USPS website allow you to see all tracking info and get all sorts of text notifications to see where your packages are at. Yes, they don't show movement sometimes, yes the USPS is the worst of the bunch, but all in all it gives you a little more info to follow something valuable coming to your home. Sometimes a little info goes a long way.
For whatever reason UPS always does this. The others leave it at the front porch where I also have a camera.

I bought my brother a Milwaukee power tool for Christmas. In the comments, I said “please leave under front porch.” They left it at the garage utility door and said “left at front door.” Didnt know it was delivered until I got home.
For work related stuff, our UPS guy is great. He does all the UPS deliveries to same businesses every day downtown so I see him nearly daily (before COVID-19.) I think he's been with UPS for ~20 years and has done his specific route for at least half of that so he knows all the businesses, their times, when they're open, etc and it's great.

USPS mail lady is nice but she doesn't come in the office to drop off mail. She'll literally stand outside of our office suite door until the receptionist or somebody else goes to the door instead of opening it and walking 5ft to put it on the front desk. Would also be nice if their schedule-a-pickup website would work too.

FedEx....ugh don't even get me started. One of the two FedEx drivers put the TV we ordered for work at the bottom of his box pile/trolley. That alone said enough for me.
UPS has been hit/miss for me lately. If the package is delivered by one of their trucks, no problem. It looks like they have a lot of temps/contractors helping them in my area and they're not as conscientious; they tend to be the ones who will either toss a package on the porch or leave it on the edge where it gets rained-on. If I didn't hear the 'thump' on Saturday, the package they left would have been soaked by the time I found it.