Freeciv

3.2.0-RC1+ civ2civ3 ruleset

edited this game slightly to add Alpine Troops and remove a Pirate Legion.

When Alpine moves against the Barbarian Leader, only get the option to Attack, and the attack does not Collect Ransom. Try Unit menu Go To and ... Collect Ransom, get message "Your Alpine Troops was unable to do Collect Ransom".

The actions.ruleset has -
attack_blocked_by = "Collect Ransom", "Capture Units", "Bombard",
"Explode Nuclear", "Nuke City", "Nuke Units"