This is a repost from my suggestion some weeks ago:

I went for the ASRock J5040 board, 16gb ram a 500gb m.2 as system using a PCI adapter , 2x4tb ironwolf as ZFS mirror pool, 350 W power supply all in the node 304 fractal case for 550 euro altogether.

Runs proxmox as hypervisor for VM or Container. 6 LXC running motioneye, plex, pyload with openvpn, syncthing, rclone cloud backup and openbookshelf.

Typical power usage is around 20W

That said it could also run on PicoPSU