Try getting into biking. I burn 1500-2000 calories (I'm not a small dude) in like 2 hours of road cycling. It's relatively easy on the body compared to running as a bonus.
Bruh unless you’re like 900 lbs barefoot uphill in the snow both ways you are not burning 1000 kcal/hr on a bicycle. Make sure you’ve input all your vital stats onto your fitness tracker correctly, and consider comparing it to a few others.
Given weight and road grade plays a role, they don't need to average 50km/h necessarily. Still, 1kcal/hour seems quite intense for a regular exercise for me, but similarly large professional-level endurance athletes probably burn far more during serious training or competitions. 750kcal/hr seems manageable to me as a non-athletic person (supposedly I've burned 2340 calories over 2.7hours once... but I was totally wiped out afterwards IIRC). 1K/hr isn't something I could maintain for more than about 1.5 hours even on the best of days.
The key here is elevation. I'm 183 cm and weigh 95 kilos, and I live in the Alps. For sure, I'm not always hitting those numbers, but throw a couple of big climbs in there and it starts to make sense.
Yes cycling is the absolute best endurance sport, and it’s fun. Swimming is also great but very few people can swim to work or swim to the bar or swim to the grocery store.
And fuck running. Your knees and ankles will thank you for cycling.
Oh also another thing to check is weather your fitness tracker is reporting active calories or total calories burned. If it is the second one it’s giving you a feel-good number that includes calories you would have burned just by sitting on the couch staying alive. If your fitness tracker isn’t calculating a BMR you can estimate your Base Metabolic Rate fairly accurately with a calculator like this one.