Gluster is a good alternative, Ceph can be prickly if you don't want a block device and instead just need a filesystem. CephFS fills sort of the same role, but does so on top of Ceph rbd.
Since GlusterFS /can use/ NFSv4 as a client, it should work with the stuff @samco_23 uses
Since GlusterFS /can use/ NFSv4 as a client, it should work with the stuff @samco_23 uses