This is not ambiguous. You can shove once per turn using an Attack Action, any ONE Attack Action. It doesn't matter how many attacks a player has, ONE of them can be a shove.
Well, given that it’s clearly been interpreted in different ways and not just by folk on this forum I think it’s fair to say it’s ambiguous. “Any one” is not synonymous with “only one”, though I agree it could be read that way. But it seems equally valid to read it as meaning that any individual attack can be replaced by a shove, which consumes just the one attack action it replaces, consistent with other attacks in the same turn also being replaced by shoves. Any clarifications I’ve found seem to support the latter interpretation, see eg
this post and
this article. I’ve not yet found anything similar supporting your more restrictive reading, but the only official-ish ruling I’ve found, the tweet I posted above from Jeremy Crawford, is only slightly less ambiguous than the original rule and doesn’t to my mind completely rule out that only one attack can be replaced. Happy to be pointed at any alternative sources that help clear things up more definitively.
It's a poor choice of wording there. Agreed.
But why would you use "one" if it means "any" or "all" or "each"?
If a character has multiple attacks it is still just one action. A second shove would only work if you get another action through haste or action surge. So having 2 extra attacks a character can attack 3 times with his one action and one of those attacks can be replaced by a shove.
Thats how i read it and thats also at least a little bit logical if i think about "shoving" someone.
Beeing able to shove more than once/round will get even more ridicoulous at higher levels. Especially for certain classes...if we get monks with flurry of blows they will run around hitting like 5 times and shoving 2 or 3 times....ehhhhh.
Even right now a fighter lvl 5 could shove 6 times with haste and action surge since they have 2 attacks/action.
Same actually goes for dash or disengage. In my understanding this is a once/round thing.
Look at thiefs. 2 BA. 2 times Dash as a cunning action. that triples the movement/round. Add haste and you run like 50m and can still attack. Imo thats not how it should be. Spells like longstrider are already next to useless. Add The added distance you get by jumping. This is a pretty big disbalance.
