It's orphaned in Debian as well, but I'm not sure what significant advantages it has over btrfs, which is very stable these days.
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Also see https://www.phoronix.com/news/Josef-Bacik-Leaves-Meta
It's important to note that striping and mirroring works just fine. It's only the 5/6 modes that are unstable: https://btrfs.readthedocs.io/en/stable/Status.html#block-gro...
I also have had to deal with thousands of nodes kernel panicing due to a btrfs bug in linux kernel 6.8 (stable ubuntu release).
The md metadata is not adequately protected. Btrfs checksums can tell you when a file has gone bad but not self-heal. And I'm sure there are going to be caching/perf benefits left on the table not having btrfs manage all the block storage itself.