About seasteading, I think that, given sufficient time, human nature will disintegrate it. It's true that communes exist, but the members of those communes are usually bound together very strongly by some common, usually supernatural belief system, often by means of force. An example is the Christian communes, many of which exist today. See, for example, the Amish and Mennonite communities. And is has been shown that, although it may appear otherwise on the outside, such communities are far from harmonious on the inside.
The problem I see with seasteading is that ego, greed and the lack of a strong, religious or cult-like binding force or belief system among inhabitants will result in heavy disputes about governance, heavy fighting and general unrest, up to a breaking point when the "mainland" will intervene and enforce order.
Even two people in a family are often unable to cohabit the same house without strong disputes and arguments, to the point of violence and divorce. Imagine what will happen when a group of several people, unknown to each other, and with lots of money to enforce their own opinions, preferences and desires, get together and attempt to co-exist in a relatively small area, physically isolated from the rest of the world...
The whole thing reminds me of Jacque Fresco's "The Venus Project":
https://www.thevenusproject.com
It may sound great, almost heavenly, on paper, but I don't think it can last for too long because, sadly, it is not compatible with human nature. And human nature is not easy to change. The former Soviet Union tried it with communism and they failed. It may sound pessimistic, but that's how we are designed.