Thank you. I've just moved it to its own plain BTRFS subvolume, now that the whole system is BTRFS. Systemd-homed still manages the home directory (storage=subvolume).
For now, physical security is good enough that encryption isn't strictly needed, but I'll probably migrate it to a LUKS-encrypted BTRFS file system for the entire installation, or perhaps cryptfs, if that becomes available for BTRFS reasonably soon. Being a subvolume simplifies backup as well. Also, Bcachefs is going to be interesting, but I'll probably wait until it's no longer "experiemntal". I hope this discussion at least gives other people ideas.