Cryptography and networking to securely communicate during organization and monitor suspicious traffic
General OSINT skills to vet people and provide proof of any claims
Not a CS skill, but common in security work is social engineering, and hell, maybe even a little bit of journalism/blogging. Build up a reputation of some sort and attempt to find sympathetic/disillusioned sources who might expose some stuff that will help protestors/organizers
Web design/UX maybe? These days a lot of people are used to or drawn to “modern” and “sleek” designs. Marxists.org will likely deter new people lol
The first two will probably be the most “useful,” but as others have stated, it’s mostly a lucrative field to make a bunch of money
However, if you want to benefit people (which won’t necessarily further any socialist cause), you can get a job at a public organization such as hospitals and schools. Some libraries are large and popular enough to warrant in house IT staff.