Best resources for navigating the meta?

I’ve been away from Arknights for a while, and I feel really out of the loop. There’s so many units now, it’s overwhelming to figure out what they all do and which ones are most efficient to build.

I know there used to be some good sites for tier lists and such, but I can’t seem to find them now. So does anyone have good recommendations for guide, tier lists, etc that can help with figuring out the meta?