It’s quite common nowadays to see leftists showing fear on social media, fear about government crackdown, about Trump designing them as terrorists, about a Third Red Scare, about civil war… And then you open their profile and there’s a pinned post for their Anarchist discord server. I'm not saying that you shouldn't use the piece of software you want, but if you believe that we are at war some changes need to be made for yours and your comrades safety. Most people aren't (I hope) planning real actions on their discord servers, as they could easily see on Discord page that they work with law enforcement.
But FBI agents have in the past contacted people due to their meme servers being regarded as Anti-America propaganda, and if you're an anarchist I'd bet a couple dollars you are spreading some Anti-America propaganda. I've also heard of similar happening to communist servers, but it was more of a mention (there's even one in the Reddit post linked) than a detailed account. If all you want is to shitpost with 6000 people without the risk of FBI phoning you because someone went too far I would suggest Matrix (with the client of your choice, element being the most common choice), you don't even need an email or cellphone to register (unlike Discord) and don't ever force you to give them your cellphone number just because you used a VPN or Tor to register or sign in. Speaking of signing in, when creating an account you will be faced with the option of choosing a server, if you don't want to use the matrix.org server, you can choose one from this list, to enable encryption on your group or in a conversation you need to go on room settings>security and privacy.
Congratulations, now you're being much more safer in your shitposts.