For example Fenn's "Supressive Fire" which at the cost of 1 strain gives all figures affected a choice of taking an extra damage or being stunned.

How does this work with the app?

Because Stunned is not as powerful in the app as normal, I don't see you picking Suppressive Fire over Trench Fighter.

If you do, use the Imperial Rule as described in the LotA manual. I would expect +1dmg to be better than stunned, so technically the figures would always get stunned (unless already stunned).

yeah took trench fighter anyway cause seems to me most app fights are close quarters so far but was wondering if there was a standard interpretation