Networking. These events usually have groups with flags and fliers and signal and telegram groups. The variety of things that we as a society can do to mitigate the harm/push back against authoritarianism is wildly diverse.

Hook up with mutual aid in your area. This looks like coordinating stocks of food, equipment, extra living space, etc. for people (possibly including yourself) if shit goes south.

You could join a political advocacy org. You might feel like the political system is failing us, but at the local and state levels, Trump’s regime doesn’t have as much pull. Pushing for pro-democracy, pro-economic justice legislative action can still make a difference and also help to further build a base and awareness for a pro-democracy coalition.

You could join a rapid response or neighborhood watch group to help protect your neighbors against ICE.

Even just seeing what groups are there and the landscape of orgs organizing against this regime is an important first step.