stubblejumper
FNG
This is really close to what I do.Heavy pack hikes mixed in with hill running have been a staple in my household, after a couple of weeks hiking speed with 50lbs is the same as without the pack and a heart rate while walking at 4mph is ~70 with the pack. In terms of purely hunt prep, I’d say this is exactly what you’re looking for since weights aren’t much an option.
the pack based workouts from MtnTough are legit, but very pricey for thelength of plan IMO. Pressing and squatting your pack or doing burpees with it is always better than nothing.
Goruck has a wide variety of exercises made to be done with a 30lb pack. Do them with 50 in your hunting pack.
If I was at a lower altitude, I would look at one of those breath trainers as well https://expand-a-lung.com/shop/expand-a-lung-3/