The other day I learned how to use a scythe to cut grass. I spent a good 6 hours outside chopping away at the grass, and started to get the hang of it by the end of the day.
There are lots of benefits to scything (no noise, no dust, no engine, no fumes, no fuel, lower cost), but the workout is one of the best ones. The most efficient scythe operators rotate with their core instead of getting power out of their arms, and they're basically doing the same side-to-side core rotation for hours on end.
But since it's so satisfying to watch the blade tear through grass, the time really flies. It's the kind of exercise that someone might only do for 60 seconds in a gym before getting bored (like throwing a medicine ball against a wall), but one that can be done for many hours without boredom when you're outdoors doing something productive.
Since my day of scything, I've also been standing and sitting with a noticeably better posture without forcing anything, will see if the posture improvements persist.
Overall, 10/10 experience. Would recommend.