Footman can equip a two hand sword and a shield.
The bug is found at the “stonehearth:armor:offhand_placeholder”. It blocks the use of the offhand slot, but since shields now use the leftArm slot, they are by passing the restriction.
Fixing the above so that the offhand_placeholder blocks the leftArm instead of the offhand results in a new bug:
If the footman had a shield before, when he equips a two hand sword the shield is deleted.