If you are considering rsync, you should also consider rclone instead, especially if you want to access cloud storage. Both are mainly for syncing in only one direction. They can be set up for two-way sync with conflict handling, but I'd consider that slightly dangerous.

Syncthing is two-way (or n-way) distributed continuous sync, devices can be offline/online at any time, and with robust conflict handling. I know it only from private use, you install it on each machine where the data lives (as opposed to accessing a cloud). It works great for that. I don't know if it is good in a multi-user or corporate context.

The truth is that that life is full of contradictions and we are all struggling to figure this one out. Not every contradiction can be cleanly resolved. In the meantime life goes on. Later it will probably turn out that we've all been worrying about the wrong question, but right now... I don't know.

Cory Doctorow's "Walkaway" may fit, depending on what you're after.

Society hasn't collapsed exactly but they are building something new from scraps of deserted technology far away from civilisation. The setting is near-future, their motto: "The first days of a better nation." It is about a group building their own bed&breakfast for themselves and others to escape from the "default" society. There is a global support network of others attempting the same. They build in old ruins with 3D printers and abandoned fuel cells.

(Another topic of the book is mind uploading. The book is all on earth, no space travel. The main focus is on politics and society and a cultural rebellion against old money. I think the main characters are a bit weak in the sense that they are too similar and I sometimes confused them and it didn't matter. But it was still fun to read for the political ideas being spelled and acted out, and yes, for the enthusiasm of building something new.)

I'd start with some basic Linux networking and tools, if you don't have them already.

I don't know if that's the basics everyone knows these days, but... learn how TCP,UDP,ICMP,TLS relate, what a netmask is, what is ARP and MAC addresses. Fire up Wireshark and look around what is happening on your network. Learn some basic commands like ip -br -a and ss (or the older netstat) so you know how to figure out which program is listening where. Learn how to manually resolve a DNS name (dig or host). How tunnel a TCP connection or a webbrowser through ssh (port forwarding, SOCKS proxy). Learn enough of the HTTP protocol so you can manually enter a valid GET request over a simple TCP connection to port 80 with netcat or nc. Or use httpie or curl for the same purpose. You can't host a lot with that knowledge, but it helps to figure out why things are not working.

I'd say Caddy is generally easier and a more modern alternative to Apache/nginx.

I guess it's only what the article says - relevant for some space manoeuvres or precise measurements, and a curiosity otherwise.

In the long run days are getting longer anyway, as angular momentum keeps being transferred from earth to moon, which is slowly getting farther away. See Wikipedia Day - Variations in length and Moon - System evolution.