Tie out

I am not a fan of tethering a dog outside for the majority of the day, for many reasons. But *some* people have a safer setup for it than others. Tethering is more about having the dog understand the tether (ie, not hitting the end of it when they see something they like). I've known dogs who strangled themselves. I've known dogs who do well enough on it. I've known dogs who are always hitting the end and getting jerked back. Harnesses are better for taking pressure off the neck, but I know dogs who chew through harnesses when unattended. Ziplines may be a better option for some dogs.

Bottom line is, there is no one safe way and it largely depends on the dog. I would always recommend keeping a dog indoors when possible, having a securely fenced yard, or having a secure outdoor kennel, above tying a dog out.

Dogs out on a chain.. and there is a reason for it being a chain and a collar (less chewable). For a really tough dog there are two collars and two snaps to the chain.

I use an outdoor 5'X10' or 10'X10' kennel outside instead of a tie out. I put a wire top on the kneel as some dogs climb. Collars have the draw backs as noted.. and harnesses the dog can (and many do) chew off. Think about how often you see dogs tied to dog houses on harnesses (rare.. so rare I have never seen one).

I actually have a outside kennel (don't know the size) but he has always found a way to escape(digging under) plus I have 3 males who fight at any given chance I can't have him just walking the yard even though it's completely dog proof. So my other dog gets left in the outdoor kennel. If I could buy another outside kennel I would or even a way to put up some kind of divider so they could share the one that we already have. My dad as is doesn't like the outdoor kennel as it "takes away from the house" I for sure can't buy another one. And the dogs use to run around the entire yard back then but now their not allowed to as my dad is "adding" to the back yard and he pees every thing in sight. So I have no other option.
My girl dog can chew her off her harness just being inside her kennel. So I see where he could start doing that. Maybe the collar is best.

It may be easier to put some ground wire down to prevent digging, so that you can use the kennel that you already have.

My other 2 dogs do use it they just don't want/find the need to dof out. But I'll look into wire on the ground as I know I've been told before about it.

I put 2'x4' welded wire under 4X6 horse stall mats in an outdoor kennel.

Flat buckle collar, martingale would be dangerous and nor secure, harness wouldn't be secure either.