Sometimes when I fly with elytra in the new 1.20 snapshots, (This seems worse in 23w13a than 23w12a as well.) the chunks will be loaded and stuff there but they are completely invisible for a really long time before they render. You can tell the chunks are loaded because you can interact with the chunks like walk around and stuff

Additionally, if you go into one of the invisible chunks, sometimes it will make all of the other chunks that were previously visible go invisible.