I did ~1.5 years of only Soylent, then transitioned into 2/3 meals per day being Soylent, which I’ve done for the last ~6-7yrs.
I’m the healthiest I’ve ever been, but it does require discipline, exercise and attention like anything else. Calories are calories and if you consume more than you burn, you’ll poop a lot and gain weight. If you drink at a significant deficit (my 1.5years was at 1200kcal/day) you will poop once or twice a week and it will take a few months of your body getting used to it for it to be more than liquid.
As others have said though, it’s a deceptively dehydrating liquid. You absolutely still need to drink water, and your water intake will largely dictate how much you pee.
It’s almost certainly related to cloud-init, (the canonical tool for handling deployment automation) or Ubuntu pro (extra long support for backporting security packages to older distros, plus some conveniences). They’re pre installed as a convenience to paid users of those services, that’s the (IMHO, quite reasonable) model they use to fund the distro. I would expect that some or all of that traffic would disappear if you disable/remove those two services.
https://cloud-init.io/
https://ubuntu.com/pro