They can work, but I wouldn't do it out of choice. Lou and I bonded two unrelated adult females for someone a couple of years ago, they already had the bunnies and couldn't get any more, so it was basically a choice of bond the females or each of them would live single for evermore. After a tricky start, the bond worked.
In fact, about 20 years ago, I bonded an unrelated, unneutered adult female pair :shock: I absolutely wouldn't recommend it to anyone now, but it actually worked - for a time at least, and that tends to be a bigger risk with same sex bonds. The bond broke down a few years later when I looked after my friend's rabbits when she went on holiday, referred aggression caused a massive fight and they never rebonded after that.