Fairislecable
My DD had a coverless duvet for my grandson, I slept with this duvet once when visiting I really didn’t like the nylony feel to it. It did wash and dry very well though.
I have a standard single duvet and it is so much easier to launder the cover and replace it and I really like the feel of cotton.
My DH has a king size duvet and cover and we have to do this together it is a real faff.
I think if you share a bed two single duvets with a bedspread over the top would ease the laundering problems.
I have often changed a superking duvet cover on my own, with the aid of 4 giant plastic clothes pegs I found on Amazon- the sort people use on the beach to stop their towels blowing away.
You just feed one corner into one bottom corner of the cover, secure with peg, repeat the other side. Then repeat with top corners.
Give a really good shake, do up poppers or buttons, shake again, done.