Bcachefs, and bcachefs on root. Need something with filesystem level encryption instead of LUKS, and *ubuntu's and derivatives have all abandoned ZFS on root installs now.
Bcachefs is a copy-on-write (COW) file system for Linux-based operating systems.[3] Features include caching,[4] full file-system encryption using the ChaCha20 and Poly1305 algorithms,[5] native compression[4] via LZ4, gzip[6] and Zstandard,[7] snapshots,[4] CRC-32C and 64-bit checksumming.[3] It can span block devices, including in RAID configurations.[5]
I see it has an audit back in 2017, but I've yet to find anything newer. The finding was good, but suggested further audit be done.
The tiered storage stuff is pretty cool. You can say "I want this data on this disk, so if I get a cache miss from a faster disk/RAM it'll come from this other disk first."
I believe it also has some interesting ways of handling redundancy like erasure coding, and I thiiiink it does some kind of byte-level deduplication? I don't know if that's implemented or is even still planned, but I remember being quite excited for it. It was supposed to be dedupe without all of the hideous drawbacks that things like ZFS dedupe have.
EDIT: deduplication is absolutely not a thing yet. I don't know if it's still on the roadmap.