Too bad, would’ve considered it as a viable option to mdadm + BTRFS.
Currently I’m using bcachefs with LVM (which can do raid, but I currently only have one NVME SSD), though it indeed does have RAID1/0/10 support. But overall I expect it not to not make the same silly default choices as btrfs, such as not being able to start the system if a RAID1 component of your root filesystem is missing. And, supposedly, when the RAID5/6 becomes stable, it won’t have the write hole problem.
It said the code base was build on something stable, but it didn’t say what, do you happen to know what FS this project is a fork of?
It’s based on bcache :) by the same author, but of course bcache is not really a file system but rather some kind of object storage layer for the purpose of caching slower block devices and absorbing write load.
Bcachefs might be coming soon to the mainline kernel, so that’s going to make it a lot easier to try out. Personally however I have lost one bcachefs (that FS was readable, though, and I have good backups), but I have also lost a btrfs before and seen reiserfs bugs, so I don’t too heavily count it against it; overall I enjoy its stability when using basic functionality. I haven’t dared trying snapshots with it yet…