Try
But not likely
Latam is not Oneworld.
Latam does not have F

You can enter the Qantas First lounge LAX flying LA J ONLY if your a LATAM Signature Black member.

I tried by politely asking and showing my OW Emerald Card. The lounge entry attendant responded politely as well and said LATAM's contract only allows for the business class side of the lounge.

We spent a little time in this OW lounge, and then moved on to the Centurion Lounge. I have been in both before and honestly think neither are worth the time. I used to use the Star Alliance lounge in TBIT all of the time and really miss it. Buffet items at the OW lounge were fine for a very light breakfast, and a coffee, but that was it. The nice part of this lounge was that it was empty. The Centurion Lounge was, as you would probably not be surprised by, as busy as ever. Filled with families and a 30-40 minute wait to get in. Had to walk around for a few minutes before we even found two seats together. Quickly determined that a walk around TBIT was the better option, especially before an 8+ hour flight to South America.

On the return, we used the DL SkyClub, and with a long 5+ hour layover, THIS was my new favorite lounge at LAX. Ill skip TBIT lounges in the future.

I was able to access the Qantas First Lounge in LAX today with my LATAM economy boarding pass and Black status, guest access included

Anyone in J on LATAM at LAX should seriously consider the Delta One lounge. LA J passengers are entitled to access on both departure and arrival and I found the experience to be excellent on our trip earlier this month. I had no issues getting access - the agents were very familiar with the rules. It is also not a particularly long walk between TBIT and T3.

I am not familiar with the Qantas offering so unfortunately I cannot provide a point of comparison.

Is it permitted for me to use the LATAM lounge at L:AX? I have a Delta SC membership, and flying (non business) on DL marketed ticket.

There is no LATAM lounge at LAX, nor is LATAM part of any alliance. So, you get to use whatever lounge LATAM has contracted with. I expect that you can use the T3 DL Skyclub with your membership, which is a very nice lounge, and I prefer it to the Oneworld Business lounge (the LATAM contract lounge for Business). Plan on a 15+ minute walk from T3 to your TBIT gate.

That's a good idea, I will do that if we're early enough. I guess we'll check bags first at TBIT.

Or if you are flying J you can use the Delta One lounge.

Greetings, everyone.
I will be arriving in LAX in LA/J, connecting on a separate ticket on AA/Y. Will I have lounge access upon arrival?
Thanks!

Last month we arrived at LAX in J on LATAM, and were able to make use of the Delta One lounge on arrival. Although we were connecting on DL to SEA, they did not care and did not ask to see that boarding pass.

Thanks for the data point. I can change my onward to DL as well.
Can I ask were you on a separate ticket for connection?

Separate ticket, yes. Like I said, they did not care about our onward flight, all they asked for was the LA boarding pass from the arriving flight.

I am not too familiar with the layout in LAX. I will be arriving from HNL on Delta One and continuing to LIM on Latam Premium business (same ticket). So I guess I will arrive in terminal 3 and continue from TBIT. Is there any security/passport check between these two that I need to account for? Or would it be fine to stay in the Delta One lounge in T3 until ~1hr before departure (I have a layover of 5 hours)?

There is an airside walkway between the two terminals, so no need to clear TSA again. Just account for the time for the walk and check what gate is your next flight, sometimes it’s on the other end of the terminal.