Ask HN: Best Security Practices for Activists?

Eight years ago I asked for advice about security practices for activists, and received the helpful advice (from Thomas Ptacek, if I remember correctly) not to disarm unilaterally, but to use a useful tool if it helps a group of activists organize well, and not to obsess about the full theoretical security of one online tool versus another. I am seeing new groups of activists pop up organized through largely online channels, including some channels that were founded way back in the early years of HN by people well known to the HN community. I use Signal now and am curious Discord (which I have never used, but which is used a lot by a group of local activists). What tools and practices should I be familiar with in 2025? How can I help newbies to activism who are also newbies to technology (the kind of folks who would never visit HN) get up to speed with best practices? What habits are useful to practice and what tools are useful to use to facilitate communication without getting nonviolent, peaceful, legal protesters in trouble just because they are trying to organize to express dissent? (How much do those considerations change in the United States with new directors in all the United States federal agencies that have investigative powers and electronic communications resources?) Thanks for any suggestions you have.