It is certainly something I have considered. There are several islands for sale in Panama. Though we are also considering movable versions of our floating homes so that could be a viable solution some day. A floating home that can sit in 5 meter waves allows you to live in a whole lot of places.
I'd imagine there were places with underwater 'islands'. How would those go for attaching seasteading to? Potentially eventually building them up to full islands?
They are called seamounts. And this is the subject of the next adventure that my crazy engineer friend is setting out on (the guy that built the seastead in Thailand).
They are useful because you can anchor on one while still being more than 200 miles from any nation which puts you in international waters.
Without seamounts it requires dynamic positioning systems which require energy.
... he needs to check out the Wanganella Bank, located midway between Australia and New Zealand in the Tasman Sea, international waters
... the sea floor rises up to 10-30 metres beneath sea surface, due to Australia continental plate and Zealandia continent, i.e. mountains on the ocean floor
... has amazing fishing and probably good location for mid-way fibre optic cable station