Just had my interview with Meta for E4/E5 role, regular SWE. I used leetcode discussions while I was interviewing and hope this will be helpful to others. Due to NDA, I will not be disclosing the questions I had.
If you look at the other leetcode discussions, it would be helpful. More specifically the last few months. Do your leetcode and coding round should be easy.

I had a mock interview (coding) followed by a screening and just finished my final interview.

Final interview was
2 coding - 2 questions each (kinda)
1 behavioral
1 system designs

Each are 45 mins. 40 mins to discuss, 5 mins for you to question them about the Meta life.

Mock interview

I was given 2 coding questions which required knowledge of how to use a stack, and the other question a common question.

Screening

Traverse a tree and do some stuff
Do stuff with some strings

You are asked to find the time complexity/space complexity and also ask what test cases you would write for them.

Final

Behavioral was more like a convo, but have a few stories lined up STAR method! Look up principles of Meta and have your stories align with those.

Coding was all arrays for me one med one hard... for each
Do the leetcode recommended under Meta and you should be fine
One round was quite interesting. I was given 2 parts of each question. Meaning 2 parts for question 1 and 2 parts for question 2. It wasn't too bad as one of the parts for each 2 questions were more discussion than writing the code.
Although the questions are kinda on leetcode, they mostly all had a twist. For example, instead of looking for the min, they want you to look for the max.
In both my round, I was not asked what test cases I would write for the questions and moved to time complexity then either discussion about the question as I finished early, or to questions I had for them.

System Design
You are given 2 options either product or infra.
I chose infra. How I prepared
I have never done a system designs interview before and is new to it. I watched videos of how to solve problems. But most importantly, look up sample questions that Meta give and read/watch them. The question I got was not a typical "Design youtube" but something more specific.

Mock interviews help a lot! If you have a friend who is willing to do mock interviews, I strongly suggest it!

My mock interview with Meta put me in my place as I was given a common question, but I struggled to solve it. As a result, I practiced all the popular questions (Although I had done them the last 3-4 months) and did wonders in all my actual coding interview!