People need to do just what you’re doing before they get a dog.
Research can save people from getting the wrong dog and it’s possible the best solution to the OP’s question is to find the dog a new home.
High energy breeds of dogs require a high energy involved owner. I’m one of those and have Belgians (perfect for me). We used to be distance runners and ran with the dogs up to 20 miles a day. Obedience, tracking, dog shows and herding rounded out the other activities. If you don’t give a dog like that plenty to do they will find trouble and behavior issues.
There are low key quiet breeds. I had a friend with a basset that was a great apartment dog and good companion. Some of the big breeds are really quiet.
You said it. Some years ago I bought a pair of Shelties bc they were so beautiful. They were my crash course on working dogs. Nothing was a game for them; everything was a job. Throw a tennis ball, and it was a death match between the pair, to establish which of them was able to successfully do the job.
Shelties don’t require as much exercise as some breeds, but they do require activity that they can interpret as work. I loved those dogs vastly, but I don’t go in for working breeds any more. Too heavy on the maintenance.
Research is essential in picking out a dog. In general hunting and herding breeds are high energy dogs that need a job. Terrier breeds can be even worse. The Jack Russell is notorious for being a handful. I’ve found the Great Dane to be one of the quieter breeds. I also love Mountain Curs. They are hunters but also just a good all around dog. Right now I have a huge Dane, a tiny Jack and a Mountain Cur. Waiting to get another Sheltie.