I interviewed with Facebook/Meta in Summer 2021. I had a positive experience overall. Throughout the process, everyone I spoke to was very friendly, and willing to help or clarify whenever I had questions. I did all the rounds mentioned here remotely, either by phone, or video call.
I was a referral and got contacted shortly after. It started with an introductory phone call w/ a recruiter to discuss what I was looking for in my career, my strengths/skills, and salary expectations.
I was moved to the next stage after, where there was some confusion w/ the recruiters after my 1st phone call where I was told I didn't need to do a technical phone screen, however it turns out I did need to do one.
After that, we got a phone screen scheduled the same week they notified me about the mix-up. In this call, I was asked my preferences w/ front-end/full-stack/back-end development, and also several technical questions on Javascript and the DOM. The questions were fairly straightforward, covering JS fundamentals like "this", event delegation, event listeners. At the end I was also asked some straightforward data structures questions about queues, stacks, and implementing them in JS. (NOTE: I did study in advance, expecting to be asked "text book" questions w/ short answers)
After this round, I successfully moved to the first technical video screen/Coderpad round with another engineer. It was around 45 minutes. I was given 2 questions, although of course they reveal the 2nd question only after you finish the first one. I found them to be fair in terms of difficulty and reviewing what others posted here was incredibly helpful. I was unfortunately not able to get through both questions in the time allotted and chock it up to my own speed/studying/prep at the time.
The engineer I was paired with was great and was willing to give me feedback on my performance, as well as answer questions about their day-to-day work, etc.
I struggle with technical coding rounds (always), but I'm rating the interview difficulty as "average", because I feel there's a lot of prep material provided and mentioned on sites like these that accurately describe the experience. The process seems fair to me and they give you adequate information to prepare well.
If you have an interview coming up and you're reading this, good luck!