Activism on the UFO front in the 21st Century might be best focused on developing sober and well documented public education materials and engaging in a variety of ways to share that in public settings, especially in the lecture halls of academic institutions.
Previous activism efforts have focused on forms of that, such as the mock Congressional hearings hosted bt Steve Bassett.
There was an attempt back in the 1990s to create a viable activism effort that had hopes of arousing a significant number of people to bring pressure for a more serious public inquiry and disclosure by the government.
Jim Moseley told a gathering crowd, as you will see from the 1st video segment of speeches from the stage at the Operation Right to Know event at the White House in 1993: “You will need alot more people”.
As everyone has likely noticed, even the big news coming out for nearly 2 years now has been greeted with anemic public attention and enthusiasm. Of course, at this moment in our history we are all very overwhelmed by the disastrous consequences of a criminal President attempting to put the story of America in a decaying orbit. Still, we are way behind the 8 ball in readying the public (and its representstives in government) by education on this subject.