I’m super late on this, but apparently Apple announced back in February that they’ll be adding support for LCP and INP as part of Interop 2025:
https://webkit.org/blog/16458/announcing-interop-2025/
Can’t wait to see how this changes our performance reports!
Aside: I wonder if this will cause a Core Web Vitals backlash… If people see how much faster their sites are on iPhones, then realize none of that data is in CrUX, won’t they complain that Google using CWV as a search factor is unfair? “Our site is actually fast, see!” Sure, we’ve had this debate already, but I think a second wave is coming—this time with charts and data to prove the point. “We knew it was bad, but we didn’t know it was this bad.” We’ll see how things shake out. (Who knows, maybe AI and the decline of organic search will make this a moot point.)