forum.freeciv.org

https://ibb.co/XDcPpG3
Why in some cities the spy don't show to option of industrial sabotage? I wanted to subvert this city wall.

There is such a thing like action enabler - requirements for the actor and the target that determine what your unit can or can't do. It is (AFAIK) evaluated server-side when your spy tries to enter a city or you use Combat-Do... menu. Maybe at the ruleset you use you can't sabotage at certain cases.