Can an enemy use The List's activated ability to target Ruin Runner?

Ruling: No. The List's activated ability requires choosing a specific unit with the named tag, which counts as targeting that unit. Since Ruin Runner has "I can't be chosen by enemy spells and abilities," an enemy cannot target it with The List's ability.

Nuances:

• Riftbound does not always use the words "target" or "choose" explicitly on cards, but abilities that require selecting a specific game object still count as choosing/targeting.
• The ability does not fall under programmatically selected exceptions because the player must make a choice of which unit with the tag receives the effect.