We got our dog a dog, and it's worked out SPECTACULARLY
My husband rescued his dog from a pound where she was set to be killed, took her home, and for years, took care of her the way people do in that slice of the world: she was fed, and had water, and went to the vet on occasion, but was basically an ambulatory alarm in a little yard to the side of his house. When we went back to his home country to get her, his mom must have asked us a dozen times if we were really sure the dog was going to live with us, inside our house. It was just that bizarre to her.
Anywho, that dog, Chocolata, has lived indoors for two years now. She house trained way faster than I expected (only used the spray bottle of Nature's Miracle, didn't even break into the gallon I bought assuming we would need it). She figured out that she's allowed on all furniture except our bed. She has four dog beds spread out around our (not that big) house. She has a crate in the bedroom. That's her safe space. She runs to the kitchen when she hears me scrape out the last of the yogurt so she can clean the recycling for me. She sits under my soft-hearted daughter when we sit for family meals. And, although she spent probably seven years sleeping curled up in the dust and gravel, she's muuuuuuch too fancy to sleep on the hard floor. Chocolata now needs a dog bed, a people sofa, a rug, or--in a pinch--a folded-up towel, or she simply can't lie down.
In these two years, she's also learned that people are good! And other dogs are ... sources of irreconcilable internal conflict. She's desperate to meet them (she used to watch the street dogs lead their happy lives, from the other side of a fence), but she doesn't know how to act around them, and also just as desperately needs to protect/resource guard her one good thing: her family, and her house. So while she'll happily trot up to the mail lady for pets, or adoringly lick any child who stops to talk to her, other dogs have always been a problem, a tighten-the-leash-and-head-for-home-type problem.
But I have always believed that only dogs are lonely dogs (they're so social--they need their pack). I've never had a lonely only dog; I've always kept at least two, and up to four, but I knew that Chocolata would never accept another adult dog. (I normally prefer to adopt adults because less house-training and less house-chewing! Plus it's harder to find homes for them, so they need more adopters.) So this time, we went to the pound and got a pound-puppy, Latte, a little 9-week-old pit/lab mix. All dogs tolerate all puppies until about 6 or 7 months of age: I figured that was the way to sneak a new dog into her/our lives.
Chocolata met Latte out in a park near our house and wasn't aggressive, but wasn't happy. We brought them home, and she ignored him. He basically forced her to play with him by doing cute bounces all around her, batting her with his paws, and chewing on her face. She spent the first week firmly putting him in his place: pinning him and growling and then stalking away. Then she started to play a little, still growling, hackles up. Then she started to chase him for a couple steps when he ran to/through/under/over her.
She began to tolerate when he tried to sneak into her under-the-nook-desk bed, the one she uses most. She would try not to let him touch her, but she didn't chase him away. Then she would let him nap with his head on her back. One morning, I looked over and he was belly-up in her bed, paws in the air, and she was standing over him, gently batting him with her front paws, trying to get him on his feet and playing. Next, she started to really play with him, even trying to start shit when he was ignoring her to chew grass outside or collect shoes inside.
Now, there's rarely any growling. They'll spend an hour together in the nook bed, "playing" in that way dogs do, open-mouthed and with a low, almost humming vocalization. They nap together all the time. She figured out tug-of-war (mostly with his leash)! They play quietly under the table when we eat dinner. They sit next to each other to chew their beef cheeks (gross, but not smelly, long-lasting, and safe for puppies). I've even seen Chocolata, the anxious dog who refuses to be vulnerable ever, roll over once or twice and show Latte her belly. She's more active, more trainable, calmer when not playing, and less desperate to always be at my husband's feet.
Latte's not even been here for six weeks, and by far the biggest and best change has been how much Chocolata has softened around the edges. I became so used to her personality that I think I stopped being aware of what a quietly-anxious dog she is. She wouldn't whine or shake, but it is also hard for her to truly relax.
With little Latte by her side (who will soon outweigh her and outheight her), she can now actually enjoy car trips, looking out the window or curling up for a nap, like a normal dog. I tried on and off for two years to train her to "down," but she wouldn't--it was just too much vulnerability. Now, with a bit of support and a bit of competition from her emotional support puppy, she's mastered it. During thunderstorms, she doesn't jump on my head and break the no-dogs-on-the-bed rule anymore, because Latte is right there, next to me, in his giant-ass bed on the floor, leashed to my wrist because he's not 100% house trained yet, snoring through all the noise and flashes. She snuggles up to him and goes back to sleep. She's just ... better. Better and happier.
It's been a reminder what a little exercise and a little companionship will do for you, even if you're well past your prime. :-)
p.s. As I finished typing this, my husband came through the kitchen to head out to the library, and I looked over past the nook bed to say goodbye to him. There was Latte, asleep in the best bed in the house, and there was Chocolata, spinning in a couple little circles and then snuggling down next to him, to sleep with her head on his back. Now they're both quietly snoring.
ETA: dog tax. https://imgur.com/a/Wir7sfk