Which handgun would you recommend to someone with little or no firearms training or experience, for home protection?

Tiger brand Wasp/Hornet spray. A shot can be delivered to the face from 20'. That should buy them enough time to escape or hopefully convince the bad guy to move on.

In my 70 years, I've been in 49 of our 50 states, over a dozen foreign countries and I've never needed a weapon of any sort for personal protection other than Vietnam. The question is, do you really need a weapon of any sort ?

For someone with little to no training, I recommend cans of wasp spray and metal baseball bats.

Training first, purchase second. Then practice, practice, practice.

get you a sawed off shotgun. no need to worry about sighting all u have to know is which end is the deadly end. most likely you'll be dead before you shoot, but you'll know you tryed. best of luck.

380 Ruger, 7+1 Accurate, cancellable, light weight and very dependable with laser.

...a handgun that's locked and loaded.

Little or no firearms training or experience? I would recommend a Louisville Slugger until you can take a proper firearms training course with you and any members of age in your household that are going to be around or have any sort of access to the firearm.
If you are going to opt to go down the lethal force route, ask yourself these 5 questions that my NRA Training Counselor asked me: 1) Are you prepared to take a human life?; 2) Are you prepared to take a life in defense of your family & friends?; 3) Are you prepared to take a human life in defense of your home and all who occupy it at the time?; 4) Are you prepared to face the legal ramifications of taking that life in defense of the fore mentioned?; 5) Are you prepared to do all of that in defense of a total stranger?
If you can't answer "Yes" to all of those questions, then a firearm is not for you. There are other "less than lethal" defensive tools out there then, such as pepper spray, pepper ball guns and personal defense training such as MBC.
If you can answer "YES" to all those questions, seek out proper training from a certified instructor (NRA, USCCA, etc) that can teach not only basic pistol knowledge but also personal protection inside the home, personal protection outside the home and concealed carry. In all, you are looking at at least 32 hours of training with those courses. Going through NRA or USCCA courses will meet the training hour requirements of most states, but a state specific block of instruction (usually 8 hours) will also be required as well. I would avoid basic courses that are non-NRA or USCCA for beginners, but that is also because NRA/USCCA courses are the most widely recognized by states who permit concealed carry and you want to be sure and get that credit.
As far as the selection of a firearm, it is like being fitted for a suit/dress. You have to find out what is most comfortable for you. Don't let the salesperson at the gun store talk you into something bigger or more powerful than what you are comfortable with. Caliber-wise, I wouldn't recommend anything smaller than 9mm for personal defense. You can go larger if comfortable and accurate, but 9mm is a good starting point for both men and women. You will hear arguments to the contrary and that the round it "too small" however there have been numerous advances in ballistics so it really comes down to the type of ammo you will be using for personal defense.
Lastly, you have to TRAIN regularly with whatever firearm you select. Marksmanship is a diminishable skill if not exercised regularly. Practice at the range, dry fires at home and even try some simulators.
My credentials - NRA Certified Instructor & Chief Range Safety Officer (CRSO)

A handgun wouldn't be my first recommendation, but for many situations it is the best tool.
In those cases I would recommend a used police Glock 40cal with a 9mm conversion barrel.
They are inexpensive, serviceable, cheap to feed, and large enough to be easier to shoot (as a close second S&W Sheild EZ 9mm).
SPEND THE REST OF THE BUDGET on training and practice.

Sadly CPT jack during remark about the 1st round being non lethal can get you in hot water. If your pulling a firearm you better make sure you understand when lethal force is needed.

Cause if during a shooting the person dies and your remark is but I used a virtual non lethal round, your where not justify. Why no one suggest you use birdshot anymore.