Leaving puppy outside

So we have a new puppy and he is a sweetheart however he was having hour long meltdowns in his pen so we gated off our living area with our 1yr old and he is so much happier, however him and our older dog are now having a field day trashing the lounge room (our older dog never did until the new pup so I feel it’s mostly his doing). What’s everyone’s thoughts on leaving them outside? We have a decent backyard and shaded area with no line of site to the road. When I look it up all I get is puppies shouldn’t be left alone for more than an hour which is simply un doable. I’m concerned he’s going to hurt himself as he’s climbing up on the couch and was jumping out of his pen, I feel it would be safer to be outside for him.