I’ll be flying GIG JFK on Delta by the end of the year and was curious what lounge Delta uses? On the Skyteam Lounge finder it only says AF & KLM use the Plaza Premium one, but nothing about Delta. Does anyone know?

Searching on the Delta website indicates it's the same Plaza Premium lounge:

https://www.delta.com/apac/en/delta-sky-club/locations

DL might only give lounge access to its passengers departing in DeltaOne (business class) since this is a contract lounge.

Does this rule apply to non-DL ST Elites+ ? DL lounge access rules have become so complicated and confusing...

Yeah hope this only applies to DL STE+. As FB Gold I never had problems getting into contract lounges when flying AF/KL/MU/KQ etc
Does anyone know or have flown DL out of GIG recently?

I don't know for sure. My status is with DL.

I would seem strange for DL to treat non-DL SkyTeam ElitePlus better than DL SkyTeam Elite Plus (GM, PM, DM, and 360). I can't envision DL check in counters having a stack of lounge invitations to give ONLY to non-DL SkyTeam ElitePlus, and I also can't imagine airport contract staff or contract lounge staff being taught the difference between DL and non-DL status in connection with probably one DL flight on most days.

When I try this link, it shows me the Centurion lounge link, although the website might know who I am.

yes but DL has different rules compared to other ST members.

I know it's weird, but for DL and ST lounges, non DL-Elites+ are already treated better than DL elites+, in order to comply with ST policies. So I was curious about contract lounges.

I hope OP reports back. I'm curious about this.

ADDED: For further context, when DL first introduced long haul international PS (Premium Select = PE), it included lounge access just the same as D1 (DeltaOne = business class) and meals that were very much like D1 but with one fewer main course choice for dinner and no pre-orders. Then it evolved with no lounge access and meals that were like coach. Now he pendulum seems to have started to swing back with PS meals that are better than coach. Perhaps DL will bring back more lounge privileges before (or connecting to/from) PS flights, at least the long haul international trips.

Another quirky situation for lounge access would be exLHR flights, where DL PM+ (but not GM, which is the lowest DL tier for SkyTeam ElitePlus) can use the VS Clubroom but DL GM (SkyTeam ElitePlus) are sent to an inferior contract lounge if not flying in D1. I don't recall clearly the VS arrival lounge requirements at LHR, although as a DM in D1, I had access without any issues. The old (sadly RIP it seems) AF arrivals lounge at CDG might also have had some odd rules, but this wouldn't have been covered by SkyTeam lounge access policies either, although again as a DM in D1, I was admitted without any problems.

If you select "SkyTeam Elite Plus Member (Other Carriers)" it shows:

Plaza Premium Lounge, Terminal 2, Take the escalator near gate B43 to the third level to access the Plaza Premium Lounge