From the article:

Futex2, often referred to interchangeably with fsync, did make it to Linux kernel 5.16 as futex_waitv, but the original implementation of fsync isn't that. Fsync used futex_wait_multiple, and Futex2 used futex_waitv. Applications such as Lutris still refer to it as Fsync, though. It's still kind of fsync, but it's not the original fsync.

So since Jan 2022, it’s been in the stable Linux kernel. For Debian and its derivatives, it would be included beginning with Bookworm.