This site has already identified two stories based on only vague memories. Here's an even worse question...
This was a TV series, probably shown on Netflix, certainly before 2020. I watched the whole season.
The general setting was similar to e.g. Lord of the Rings - a medieval, rural sort of life, without advanced technology. I don't remember whether magic was involved. I think there was a royal family.
At the beginning, a bunch of teenagers were training for some challenge to determine which one or several of them would be chosen for a special quest. I think the main protagonist was the only female, or one of very few, to attempt the challenge, and the rest mocked her for it. They might've all been elves. They certainly lived in a place with a lot of trees.
I don't remember what the quest was for. At the climax of the series and the quest, the group found a massive, ruined, futuristic city. It may or may not have been what they were expecting. They may or may not have found what they were looking for. The lighting was probably coloured red-orange.
After spending a whole series getting from A to B, they took only one jump cut to get back to A again - coming out of a cave, I think. I'm very sure about this detail because I remarked how silly it was.
The cover or intro sequence probably used a lot of light blue colours. It may have had a theme of things intertwining or weaving together, and a woman singing indistinct words, or I might have confused that with a different intro sequence.