UA customer is 2nd, your non-UA/US *G card is the most important. And remember if you don't have your A3*G card with you then most likely you won't have access.

I have a related question and not to open another thread, I'll post it here.

I'm *G (SuperFlyers card) on ANA, fly on several StarAlliance members and credit my miles to Lufthansa (general member) because the miles expire on ANA and not on Lufthansa (got their credit card).

I flew recently with Turkish and I was told I cannot credit the miles to Lufthansa AND use the +20kg Gold perk that I got on NH*G. They argued that they could not justify afterwards why I was allowed the excess baggage and that I have to register my NH FFP for the flight. In the end I had to credit the miles to ANA. Sounded reasonable but I'm still in doubt. Is this the norm?
I'm saying this because I had no trouble accessing the lounges (never tried the baggage perk though). They just ask me if this is a mistake and after I explain to them the situation they just let me go through.

Welcome to FT, Megadeth5150

I'm not really sure what the technical rule is--the Star Alliance rules generally talk about *S/*G members but don't mention whether that has to be reflected in your reservation

That said, flying US-domestic with US and UA, I've had this come up several times. US has always been happy to waive the fee after just looking at the card. UA has generally also done that, but several times they insisted the *G status must be reflected on the reservation for the baggage rule to apply. In that case, I let them put it on, then walked to the lounge and asked them to change it back to the program I wanted to use for credit

When TK said that to you, was that at IST or at an outstation? When UA played that game with me, it's always been at a fairly small station and I got the impression that they didn't know how to--or want to bother with--override the computer to waive the fee. At larger stations they glance at the card and don't say another word. If you were at an outstation, maybe they were just reading off the screen

Matches my experience also

That's an interesting option, I'll have to try it. But, I'm usually flying out of NRT and I'm reluctant to do that at the NH lounge, it might red flag my account and if they cancel my SuperFlyers card, I'm done for (I don't travel that much anymore and I wouldn't be able to reach Platinum NH*G with them again). Or maybe I'm just paranoid. I might try it at the UA lounge at NRT.

This was at NRT, with Japanese staff of course. I argued that for the lounge, one only needs to present the card and this should be the same for the other perks as well, but their reason sounded more plausible.

That sounds like a good approach. I was also changing the credit-to program to the operator of the lounge and the flight. It's hard to imagine them refusing to do that. But going the other way around and wanting to keep the benefits, I could see there being some pushback

The first couple times I also tried that argument. It never worked--nor with the supervisors. So I ask them not to change it, but if they insist, I'm happy to let them do it and then find a way to change it back--knowing that I might not always succeed

It would be great if there was a Star Alliance rule spelled out on this, but somehow I doubt bringing a copy of that is gonna change what happens at the checkin desk. You could, however, opt to simply pay the baggage fee and ask for reimbursement later. Risky

For sure, despite where the miles are being credited, you need to simply present your Star Alliance Gold card and lounge access will be granted

If you are flying UA then you can change it at the UA lounge, if flying NH need to change it at NH lounge, or for any airline change at the gate.

There aren't any *A rules preventing doing this, indeed many *A airlines have 2 FFP fields specifically to cater for it (FQTS for status recognition and FQTV for mileage accrual). It is possible TK system required the *G status or fee charged, or possibly more likely the agent didn't know better.