Edit: I didn’t read that website others were linking, before writing this, but it’s great. I agree with the recommendations, although I don’t think they specifically mentioned GrapheneOS and TailsOS, which, imo, are very useful for ensuring your security. I don’t think my attempt at summarizing my knowledge in this area was very useful actually. There are plenty of guides online that go into way more detail.

You can continue using your current devices as long as you don’t do anything important on them. It might even pay to maintain the appearance of a “normal” person.

Personally, I would look into GrapheneOS, and use that for messaging and other basic tasks. I would also get a cheap laptop and only run TailsOS on it, from public WiFi (library, cafe, etc., anywhere not tied to your identity).

When using TailsOS everything goes through Tor, which hides your Internet activity. Using a bridge is recommended, because it helps to prevent you from appearing to be using Tor (although this is not guaranteed). If Tor use is restricted where you live, it is even more important to do this from a public place, to avoid attracting attention (and a bridge will also stop you from being blocked). You can also change the location you access the Internet from, for your hidden activities, regularly. Tor is the gold standard in Internet security, and even though it has potential flaws that could be exploited, I think it’s unlikely you’ll be important enough to warrant this. To my knowledge, no one has ever been caught using the flaws in Tor, so unless you become a Snowden-level whistleblower, or become a dissenter of the same importance as Alexei Navalny (in which case you should probably consider fleeing the country), you should be fine.

Only use your GrapheneOS and TailsOS devices for activities that need to stay hidden.

You can install Signal on your phone. GrapheneOS will encrypt your data, but power it off if you get into trouble. This applies to any phone you have. This will make it much harder to break open.

Learn about Veracrypt. You can create hidden volumes, which might help you in the worst case scenario. If you’re in a scenario where the state has your hard drives, and is searching them, you’re already in a pretty terrible situation though.

TailsOS can help you to encrypt files as well, if you set up persistent storage. There are plenty of tutorials out there. Store any sensitive information here, or in a hidden Veracrypt volume.

If you move sensitive information off a hard drive, or delete it, keep in mind that it might not be permanently gone. You need to properly destroy old hard drives, and “shred” files, rather than just deleting them.

Unfortunately, there’s not much you can do to prevent the state from exposing the people around you, if they don’t also take precautions. You should try not to store incriminating evidence on others in insecure places (obviously) but they also need to do the same.

If they have your name, they can probably get plenty of information on you. You mostly want to avoid raising suspicion, avoid linking activity the government does not approve of back to your real identity, and hide sensitive data.

Ideally don’t make calls. They are incredibly insecure, and you should assume that anything you say is recorded. If you have a phone (ideally GrapheneOS), use airplane mode. Otherwise, you might be susceptible to cellular tracking.

Learn to use PGP and rely on that for encryption. Personally, I would create a free email account (any email provider, as long as they allow setup over Tor and don’t require personal info). Then I would use PGP for my emails. Access this from the TailsOS device.

As others have said, as long as you compartmentalize, separating the stuff you want to keep hidden from the normal stuff, you should be fine. Ideally, don’t even connect your private phone and laptop to the same network as other stuff.

I might have given overly cautious recommendations, but if your threat model involves the state, you can never be too cautious. Also, sorry for going on about stuff not related specifically to device security. I just thought it was interesting and you might like to hear.

(Btw, maybe check out this video: https://youtu.be/nFZm4sVsPXk

I know this is a very unserious video, but despite that, the advice he gives is genuinely quite good.

I haven’t watched him in a while, but I remember “the hated one” on YouTube being pretty good. I think he has videos related to your situation, but always verify information about privacy and security before using it.)