Tips/ideas for at-home DIY activities and enrichment for my GD

Quick background:

• 5yo
• In great health so far
• No allergies as far as we know
• Gets tired quickly, around 10-15 minutes of play time, but recovers quickly–he's usually ready to play again after a 15-30 min rest.
• Food-motivated but sometimes picky with treats

I’m looking for ideas to keep my GD entertained at home. I feel bad leaving him alone for a few hours when I run errands, and even when I’m home, there are times we can’t go out due to work or weather.

He hates the rain, and on sunny days the concrete and sand gets too hot for him, so we only have a small window where he can safely run off-leash. Our usual beach spot also gets crowded, especially on weekends, holidays, and even certain times of day, so while I still walk him, he doesn’t always get to run freely and burn off energy.

He’s well-socialized with both people and pets, but I keep him on leash around other dogs because he gets overly excited and rushes at them to play. Most dogs don’t react well to a giant charging at them, so I have to keep interactions controlled, which limits how much he can really tire himself out.

He’s older now and generally chill, more of a couch potato, and used to a smaller living space. Still, there are days when I can tell he has pent-up energy and needs more stimulation, and I want to give him better outlets despite our limitations.

The issue is, he gets bored easily:

• He has a lot of toys, but loses interest quickly or destroys them
• I’ve tried DIY enrichments (like wrapping treats in paper), but a lot of times he'd figure out a way to cheat it–like eating the paper or destroying whatever DIY we've set up
• He doesn’t care about TV or music
• Even a Kong with peanut butter only keeps him busy for about 5 minutes until he decides it's too much work for him

I also have a cat (his “older brother”), and while he tries to play, he’s just too big and strong, so he usually just pisses off my cat.

Right now, the only things that work are:

• Soft omelette or peanut butter on a lick mat
• Treats wrapped in a knotted blanket (which he recently started tearing)

Both only keep him busy for about 15 minutes, though, and I’m hoping to find activities that last longer. I’m open to food-based ideas but want to be mindful of his diet and weight as he gets older.

Would really appreciate any ideas, DIY or store-bought, that can keep him mentally engaged and entertained longer. Thank you very much in advance!