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

.88 Magnum
https://www.youtube.com/watch?time_continue=27&v=aQvtfHJZTUc&feature=emb_logo

If you're going to use a weapon that fires a shotgun shell before it fires a .45 round to give some kind of warning; then I suggest a Mossberg 12 gauge shotgun. If you keep the chamber cleared, racking a round into it when someone breaks into your home is warning enough.

Get training first. it will be fun. Then look around at stores if they even have inventory. BTW, we have multiple options in my home. We have a large dog and an alarm system. also, We live in bear country so bear spray is in each car plus large canisters at front and back doors stored discretely. Most situations can be addressed with a huge cloud of pepper spray and the best thing is that everyone goes home. If I am ever trapped in a home invasion, we have several options in our safe room. Remember, humanity has only flourished along side our canine companions so have a dog. (I am a veteran but also a 20 yr defense attorney. Bad guys hate dogs. even little dogs create chaos before they even get near the house. Big dogs are terrifying to bad guys.)

I would recommend that they take CCW course at a range with a certified instructor . When they have successfully complyede the courses, then repeat the range work wth the same instructor with a variety of handguns approved by the instructor. WaynePrice

As a former firearms instructor, I have to say if you have no to little experience with a firearm, you should not have one. To much can go bad. You must know everything about your firearm. How it kicks, how it shoots, how to handle it, what it feels like. If you don't you can hurt yourself or an innocent person or family member. Enroll in a firearms course. learn all you can it can and will save a life.

Spot on. Leave all that to CERTIFIED PROS, nothing else AT ALL!

I would suggest a 12 gauge shot gun, if you really want to hit an intruder.

I completed gunsmithing school in 2015. During the last six years I have answered this question many times.

Elderly people, especially women, don’t have the grip strength for revolvers above.22 caliber. The oldest firearm revolver available in.32 S&W stopped being manufactured in the 1930s.

For elderly shooters I recommend a .22 caliber Browning BUCKMARK or the RUGER Mark IV target pistol. Easy loading magazines, easy spring tension to cycle a round into the chamber, low recoil energy because of the mass of the pistol. Drawback is the weight might require a two-handed grip to shoot.

For everyone else, pick your scenario. Back up you want the Revolver in 1 1/2 inch barrel in S&W .38 Special +P. You suffer recoil energy but then again it is a backup and when the chips are down, you want to rely on adrenaline and hot lead in your favor.

For COMBAT SITUATIONS (like Law Enforcement and Military Mortal Combat), the 9mm is proven... and if more knock down is desired you go for SEMIAUTOMATIC in .40 caliber, 10 mm, or .357 Sig.

No pun intended; but that's a "loaded" question. It depends on various factors.
The MOST CRITICAL is to ensure that some reasonable amount of training is taken - a Basic NRA Handgun Safety Course, AND some serious discussion on the legalities of lethal force.
Age, size, confidence level and more. In the case of handguns, generally, for anyone who has no experience, I recommend a revolver. That avoids issues caused by lack of experience regarding routine maintenance, and mechanical problems that experienced handgunners know how to overcome with semi-auto handguns. As for calibre, for seniors (particularly the frail, or females), a .22 will do and the caliber should not be underrated. After all, WHO wants shot with a .22 (ask Robert Kennedy for his opinion)? Indoors, the sound of a .22 is as threatening as larger calibers.
For those without size/stength issues, then a .38 revolver with single jacketed hollowpoints -- DEFENSE rated as opposed to DUTY rated. Weather is a factor in regard to heavy clothing - some hollow point ammo when used against a heavily clothed (winter) person, may not have a required penetration. A MAJOR concern too regarding penetration is whether or not one resides in a single camily home - no one wants their shot to penetrate a wall into a negihbor's residence, like in a duplex or apartment.
For a long gun, a shotgun can be a practical choice and even a 410 SG will suffice; especially with a variety of ammo. Standard shotgun rounds followed by ball loaded SG rounds. Again, for seniors or others with small hands or frail conditions, I suggest avoiding heavier (12 gauge) shotguns. Similarly, pump shotguns require some serious range time for those with little or no experience.

My father used to own the Judge, a 45/410 revolver. It is better than most for self defense and as long as you point it correctly will put the assailant down. This assumes you have had weapons training prior to purchase.