Well that settles the main question pretty decisively. 

This IS in the same nest of timeline(s) as Luna Lovegood and the Chamber of Secrets [? · GW] and it almost certainly isn't from the first loop (she's already forgetting things)... but since Cho can ask Luna to ask SMITE club to attend a concert, Luna's memories and linkages to that organization still exist "in time" for this timeline.... so this might not be from the last loop either?

Two years ago it was no Muggle artifacts in battles. Last year it was no electronics. This year the restrictions are even stronger

Maybe: Harry gets the first year, Luna gets the second, and now Tracey gets the third? If there are four more stories set in four future years, I would not complain!

Emotionally, I was hoping that this was part of Luna's final loop and also chronologically later than Luna's final battle so somehow Luna could start to make friends who actually survive to continue as her friends?

EDIT: Actually, the more I think about it, the more I feel like my theory of time here doesn't definitely survive contact with all the hints. I think the calendar date here is LATER than Luna's final surviving timeline's boss battle, but the history seems more like the history from before that final battle edited the timeline... maybe in this timeline... Maybe here... Luna's enemy is still out there, and still hunting her, but it will somehow attack later than it attacked in other versions of history? I think I'm still confused but my curiosity is certainly piqued <3

"Are you about to invite me to join a secret organization full of interesting people like yourself?"

Is this after the concert in part 4? Does Tracey not remember it?

"plan music" did you mean "play"?