I’m no expert, but I think KeePassXC doesn’t need to sign in to a server somewhere.
koreader is my goto reader, on my tablet and phone. The interface is a bit unintuitive, but once you get it set up to your liking, it’s a great reader.
I just have some syncthing shared folders with friends/family. It may be a little weird to set up, but once there, it’s seamless.
My grandmother ran Linux for a couple decades until her death at 101 years old. My 80+ year old mom has been running Linux for at least 2 decades. Yes, I’m tech support, but I don’t really have to do anything. It just works.
I recently read Kernighan’s UNIX: A History and Memoir. It was pretty interesting. Also, Bell Labs still hosts a page with a lot of links/info for Richie at: https://www.bell-labs.com/usr/dmr/www/
There’s this: https://github.com/lextrack/Simple-Screen-Recorder
Disclaimer: I haven’t touched Windows in at least a decade.
That was my thought as well. I’m also thinking it might be a challenge to get something to read them in 100 years.