To me unions solve an asymmetry where companies can fire a worker more easily than a worker can lose their job. So personally I'm not interested in a union of all programmers, as that would create a power asymmetry the other way.

I'd more thinking about a professional organization like the AMA, the assorted bar organizations, the society of professional journalists, or the various engineering societies. Basically I want an organization that can set forth reasonable professional ethics, do advocacy and education, and act as our collective voice to back up individual engineers who refuse to do something unethical.