Here’s Johnny! 3 years old, USA. What is he?

We’ve had Johnny for almost three years and rescued him when he was about 4 or 5 months old. In Midwest USA. Somewhere around 65-75 pounds. The top of his back is just about knee height compared to a 5’10 adult.

Very intelligent, very energetic (zoomies every day), has a major attitude problem but he’s total sweetheart cuddle bug too, loves the snow but loves laying in front of a heater just as much, loves digging in the dirt and chasing animals, but usually not fast enough to catch anything, too big to be a lapdog but not big enough for us to discourage his delusion that he is one. SUPER chewer! You name it, he can chew through it and probably has. He’s very expressive, especially in his ears.

The rescue that found him abandoned wasn’t completely sure, but told us boxer/lab mix but possibly a mastiff/lab, and we haven’t bothered to test. Now that he’s fully grown, I don’t think mastiff is right, and I don’t know about boxer, but I do agree at least part lab. Family/friends and every vet who’s seen him have had different guesses of combinations, so I’m curious what other people think!