You can absolutely find non-performative posts on Instagram. There is value in a sincere post - ex. sharing pictures of your cat to your friends.
Whereas in LinkedIn no such value exists in my experience - I can't imagine myself posting there for any other reason than to be performative.
So in terms of % of posts being performative I don't think anything tops LinkedIn.
You can absolutely find non-performative posts on Instagram. There is value in a sincere post - ex. sharing pictures of your cat to your friends.
Whereas in LinkedIn no such value exists in my experience - I can't imagine myself posting there for any other reason than to be performative.
So in terms of % of posts being performative I don't think anything tops LinkedIn.