iOS15
Since we focus on last click plus source of truth reporting, iOS15 won't affect us. As long as your URLs continue to be tagged with UTM info properly, we'll continue to have one of the best last click attribution data around.
With regards to FB reporting, we've always been strictly reporting on last 7 days click attribution window, which will continue to be the only valid ways of looking at FB performance data as privacy restrictions tighten. We recommend to switch any ad platforms that are mobile traffic heavy 7d click-based reporting (unless it's very desktop heavy).