The queue is the easy part
Talk to the person who also arrived two hours early. Trade one actual opinion about the support act. That is enough to be recognisable at the barrier next time.
The hard part is not losing them after. Instagram is a weak gig graph. A diary that shows shared shows is a stronger one.
Find overlap after the night
Radar shows friends who were at the same gig on past show pages, and shared gig counts on profiles. That is how “we keep bumping into each other” becomes a list you can see.
Free direct messages mean you do not need another WhatsApp group for every bill. Pro event chats help when a whole crew is going.
Taste match without being weird
Do not open with your full diary dump. Share one upcoming gig you are both likely to want. If they log it too, you have a real overlap.
Concert friends last because the hobby is expensive and specific. Logging the night is how you still have the receipt.