If it was me, I would not run Lemmy/Piefed in your situation. These things are designed to be fully open and visible to anyone who want to look at them. Probably not your use case.
I'd rather look at something like a Matrix instance, where you can have encryption and secrecy built in. Also, you say that you're a noob in these things. If you want to hide from the government, you really do need someone very experienced to help you with security, or else it won't end well.
All the best!