Distributed computing. Its amazing to see things go from isolated PC to things like p2p torrenting and BIONIC to block chain and IPFS to kubernetes to the fediverse and Matrix and Tor.
All filling wildly different niches of trust and capability.
Want to run a secure shared virtual reality space in p2p way? Check out 3rd space built on the matrix protocol.
Want to build a highly secure computer system spanning regions and dataceneters? Check RKE2!
What about just a secure little thing in your house or across friends and family houses? Not gonna believe it but rke2 or its simply brother k3s.
Just need to store public data? Chuck into IPFS and share it in a highly cooperative way.
Want to push it out in a pub/sub fashion or sub to others info? Check out ActivityPub. Great for medium trust networks since you can choose who you publish too or subscribe from.
Maybe you want to share just metadata between private servers but real time data between users, check out matrix.
Maybe you want to share data publically but what hard incentives to keep the compute and control of that distributed. Check out block chains and pick your poison of incentive models (e.g. pow or pos or maybe look at the wierder ones). With current pick of creating a limited supply digital asset to act like currencies do.
Maybe you just need a VPN you can trust, maybe try a distributed network of volunteers using layers of obfuscation to minize info leaked about your network.
Plenty of human problems around all of these but still super cool how far we've come.