Gemini [0] is one. It's basically a vertically integrated HTTP(S)+HTML+CSS+JS replacement for the indie web that solves a lot of issues of modern web stacks... by doing away with most of the features that aren't needed for a 1998-style Web. It's meant to supplement WWW and not to supplant it.

Gemini is purposely designed not to be extensible, and to omit features that would allow the plagues of the 21st C, such as user tracking, fingerprinting, resource-hungry and bloated clients, excessive interactivity via JavaScript etc., to be a part of the user experience.

Despite that, it's pretty usable. Creating a Gemini site is not terribly complicated, and if you don't want to use Gemini's native markup language, you may use something like Markdown instead because many Gemini clients support that. Interactivity may be added via server-side processing, just like CGI.

One of the most technically impressive/surprising solutions in Gemini is how they leveraged TOFU [1] and TLS keypairs to provide an optional decentralised user identity protocol that effectively obsoletes the need for SSO - because the browser can automatically log you in via your TLS keypair.

[0]: https://gemini.circumlunar.space/

[1]: https://en.wikipedia.org/wiki/Trust_on_first_use

kappa architecture db(s), gossip protocols like secure scuttlebutt, garlic/onion routing protocols. I didn't really look at how "new" they are what with Ecclesiastes and all that.

But the question is great, what problem spaces are hot (or need to be!) and how can a deep understanding of algorithms and game theory solve them? How can we bridge the gap of large scale manufacturers with small scale production needs? How can we heal the wealth gap between us and the global south?

I'm hoping the answer involves at least a little category theory myself.

I found great enjoyment in reading the spec for the double ratchet mechanism. So interesting.

https://signal.org/docs/specifications/doubleratchet/

That "protcols" in the title.

Not to nitpick, just to make it findable should someone search "protocols".