You could just install a minimal Debian system and install what you want after that. I use Nextcloud on my media Center for example. If you just want a Windows share you could instsll samba. If your Linux you could use ssh or nfs. Or could use Syncthing. All of these are pretty standard.

The big question is do you want raid. If so you need at least two storage volumes.

TrueNAS

Another vote for TrueNAS core here. Have been running it for a couple of years with no major issues.

Proxmox

Edit: Installed as the hypervisor on bare metal and then whatever you want to try out like OMV, Plex, jellyfin, syncthing or cloud software in an LXC or VM

TrueNAS Core.

I've used Rockstor in the past, I liked it mostly (but in the end went with a self-configured OpenSUSE system).

Apart from that, I hear good things about OMV and TrueNAS

Openmediavault is quiet simple and you can also run docker containers on it