Reach out by a Meta recruiter. All questions were leetcode tagged (or a variation of it).

OA (CodeSignal):
1 Easy + 2 Mediums + 1 Hard

Technical Round 1:
Problem 1: Convert BST to sorted doubly linked list in place
Problem 2: Merge Intervals (variation of #56 seen here)

I got problem 1 and suboptimally got problem 2 (nlogn vs n).
Interviewer was pretty nice overall.

Technical Round 2:
Problem 1: Nested List Weight Sum (exactly #339)
Problem 2: Variation of the Basic Calculator problems but with only "+" and " * " operators.

I optimally got problem 1. Also got the optimal time with problem 2, and optimal time + space with a followup on problem 2.

Interviewer was also friendly.

Behavioral Round:
STAR is pretty much all you need to know. Questions on most proud project, then a time when I disagreed with a design choice and how did it affect, followed by time when I had limited information on a problem and how did I proceed. Final question on what I feel I lack and can improve - question developed based on pointers I brought up in the 2nd and 3rd question.

Overall a pretty seamless process.