To understand your comment correctly: What does "these islands" refer to? Walled gardens that we create ourselves using the open source frameworks?

I think probably things along the lines of what's been called the 'cozy web': networks of smaller groups that don't publish to or expect responses from effectively the entire internet as a whole. (This kind of thing has always existed, it's basically the group chat with your friends but perhaps slightly bigger, but I think there's a bit of a trend of focusing on it more because of the feeling that the twitter/facebook attention and feed model is bad for your mental health. I've always felt the twitter model especially was pretty cursed so I'm glad there's some agreement building there).

It's still a work in progress of an idea.

I'm thinking more like mesh networks. I spoke of Reticulum elsewhere in this thread, but here I'm thinking I'd like the ability to easily join multiple TCP/IP networks (islands of connectivity) by social group (my friends) or by interest (pirate file-sharing group, my work intranet, a knitting community with their own IRC server, FTP, etc.).

Basically easy-to-use private & encrypted LAN overlays on top of the public internet. Each operator decides who to allow in or kick out of the network.

Wireguard solves the most of technical challenges, but it needs a frontend. The biggest concern probably is most software broadcasts their stuff across all interfaces, defeating the point of isolation between networks.

The purpose of The Inter-Network, or internet for short, was to connect together precisely these "multiple networks" that you refer to.

It's failed because of CGNAT, but come back because of IPv6.

Thanks but I am talking about the complete opposite of connecting multiple networks together.

I’m not sure why we’re talking past each other. CGNAT has nothing to do with the public web dying because it’s both too large, too spammy and too juicy a target for mass surveillance.