Finishing the Imperial Radch sci-fi trilogy (Ancillary Justice/Sword/Mercy) by Ann Leckie. Despite the agender language feature (everyone is addressed as she) the books deal more with colonialism, imperialism, and personal identity, rather than gender. Writing style is very information-dense, lots of thoughts and actions happening simultaneously. Compared to other science fiction that I read, it gets much more into the cultural and interpersonal situations, especially the second book.

Revelation Space series (specifically the “future” part: Revelation Space, Chasm City, Redemption Ark, Absolution Gap) might not have the best writing, but the wild (and sometimes insane) ideas and scale of everything is great.

Late Soviet Union might be a similar to what you are looking for? I wasn’t alive back then, but from what I recall from reading old science magazines as a kid, there were few home computers, lots of “radio-hobbyist” stuff (DIY electronics from radio to computers), and praise for “inventor and rationalizer” for the good of the people. On paper at least. I think most interpersonal communication was over the phone or amateur radio, or even telegrams.

I don’t know much about how modern China goes about it though.

But TBF it’s very difficult to speculate about message encryption. Thinking back from my own experience, digital communication (over the internet or even SMS over cell phone networks) was not common until 90s-2000s, and encrypting them became a concern not too long ago, early 2010s I think? Before that, it was HTTP (without the S) and unencrypted AIM chats over the Jabber protocol.

Another interesting exploration is in Light of Other Days by Stephen Baxter. New technology allows creating light-passing micro-wormholes at any location (and time!), erasing privacy nearly entirely. At first, tabloids run wild with “shocking” photos of famous people, but eventually the hype dies. There are people who outright do lewd things in public (“anyone can see me at any time anyway”), some go about their life as usual, and some join secret groups who meet in the dark and use touch language for the deaf-blind.