One possible group on Reddit to reach out to are the people doing /r/50501 - they're organizing a large protest on Feb 5th, but it looks like a continuing resistance movement. They have more visibility on platforms outside of the Fediverse, but it's only a matter of time before those platforms begin to throttle their visibility.
If they also grow a 50501 community on the Fediverse, when the throttling inevitably happens and the news pays attention to it, both their movement and the Fediverse will get a boost. They'll probably lose their ability to organize on Reddit, but they will win more followers and help develop a better social media system.
If they promise not to link back to Reddit, I'd like to host them here.