I spent a vacation once with no internet and no lights. Worked myself hard all day snorkeling and went to bed at dark.
Every night, woke up in the middle of the night for a peaceful amble to the jakes and wandered around for a bit enjoying myself before going back to bed.
What I currently do, as because of health I sleep two shifts
Wake up slicked with sweat, drag my decaying meat husk out of bed. Dry off. Use bathroom, talk to a cat who loves affection... when you're in the bathroom. If it's near dawn, go outside and water the plants. Come inside, wait for husband to wake up. Eat lunch, plan dinner.
Go back to sleep.
Sibling gets home, I'm either awake or will be woken up. Make dinner. Spend time with husband, go back to sleep.
I didn't do it on purpose. It just happened. I guess living out in the sticks does help: it's not like we don't have electricity or internet out here, but the first neighbor is 3 miles away, the town is 5 miles, and we have real starry nights here. So it's quite easy to turn off the light and experience a, quiet peaceful night at the hours at which sleep should be happening naturally.
I fall asleep around 8 or 9 pm and I wake up around midnight or 1am, watch something quiet and peaceful so I learn something interesting without falling fully awake - and more importantly without waking up the missus - then I simply fall back asleep until 5 am.
I live above the arctic circle, so when it's winter, I usually sleep longer. And when it's summer and it's daytime all night long, of course I sleep less. But on average, I sleep 2 x 4 hours per night. I feel just as refreshed as when I slept 1 x 8 hours. But perhaps feel less "disconnected", if that makes any sense.
I once had the perfect job for biphasic sleeping. I would get up at 4 AM, work and be home by about 1 PM, sleep til 4 PM, stay up til 11 PM, then back to bed til 4 AM. 8 hours of sleep a day, 7 or 8 hours for work, 7 hours in the afternoon and evening for whatever I wanted, and I felt well-rested the whole time. It's the only thing I miss about that job.
Personally I find biphasic sleep pretty normal and easy to do when I'm working a job in a timezone that's behind mine by a few hours.
Go to bed at 12:30, sleep 4.5 hrs til 5:00, wake up with the cat at dawn, take them outside and enjoy the morning tranquility for a bit, go back to bed at 6, sleep til 9, get up to start my job at 10 or 11.
I don't do it when I have to be up early though, I both always struggle to go to bed early, and I find waking up and being up in the middle middle of the night, to feel more stressful than doing it at dawn.
Tidying up, journalling, writing, or art. Though nothing on a screen and nothing related to eating to avoid brushing my teeth again.
Indeed, I have the means and curiosity to try out biphasic sleeping. Only things that keep me back are having two alarms a night (at least while I'm not used to it) and the fear I'll get too worked up to fall asleep again.