If, for example, you want to be able to “organize” and plan “political actions”, you ideally want to use public networks to recruit, then use some sort of end-to-end encrypted network for the planning actual events. On one hand, I’d say you want those networks to be authenticated, so you know which individuals you’re sharing info with; but on the other hand, that could make it easier for a powerful foe to mop up the participants. So maybe encrypted but unauthenticated and deniable.
100-150 years ago, people met clandestinely in various locations for such purposes. I think one would need to read through history and try to figure out what people did and why they did it, as well as how well those things worked. Only then might one be able to design a digital analogue that met those same requirements and was impervious to some of those weaknesses.
Note that I am not telling people how to be subversives. As a federal employee, (despite being off-work since late last year and likely until some time next year, I am still currently employed by them,) I do not and can not endorse or support such things.
I am just saying that many people were drawn to the Fediverse by advertising that was demonstrably false, and that they thereby obtained expectations of privacy and security that are also false.
None of us are perfect about this, but we should not post anything on these networks (even by so-called direct messages) that we would not stand up and proclaim on your nation’s most watched and listened to nationwide broadcasting networks and streaming channels. Direct messages are not secret (not encrypted, so at the very least, instance admins and database admins of all involved servers can read them ... although you should trust your admin or move to a different server).
I’ve heard of people sharing their physical locations, their meatspace handles, their employment information, and even banking / payment information via these fake DMs. (I’m not talking about a Patreon / GoFundMe link. Those are meant to be shared publicly.) No! Get yourself an account with an e2ee chat provider and use that for all such messages. These kinds of networks are not suited for such things.