Asking as I've got a lot of spare components lying around that I'm planning on turning into a NAS. If it doesn't work out I'll buy a pre-built enclosure and reuse the drives.
I've been running a XigmaNAS system in an ancient xeon workstation enclosure I bought off-lease. It has been ok, but I think next time I'll use a Linux based solution so I can also run docker and other familiar tools.
I've been reading Brian C Moses' diy NAS series for years and haven't yet pulled the trigger.. but this might be the year!
My workload is primarily nfs and iscsi; I have a cluster of rack mounted raspberry pi 4s running pods on k3s with nfs storage volumes, and have been experimenting with netbooting then so I don't have to deal with USB or sdcard media failures quite so often. There's also a desktop volume share via samba for my family. All backed up via duplicity to backblaze b2.