Join Date: Nov 2018
Location: Istanbul, Turkey
Programs: TK Elite Plus,BAEC GGL,ITA Executive, AFKL Gold,QR Gold,HH Diamond,Bonvoy Gold,ALL Gold
Posts: 14,186
In the USA, QR check-in desks tend to open 4 hours before departure.
It's very likely that the check-in desks would close at 18:30 until 21:30 as in outstation the check-in agents would proceed to the gate when the 19:30 flight is boarding. QR does use the same agents for check-in and boarding.
By the way, if you're not an AA Admirals Club member, you wouldn't be able to use the Admirals Club without a boarding pass. If you're a club member, your same-day arriving boarding pass would be sufficient.