Can I build a NAS out of a desktop? [Request]

I'm not sure I can recommend anything without knowing your goals. For me my needs quickly outgrew my little mini PC and now I have a cluster with a few single board computers. Here's a basic list of what I run:

Dell workstation (proxmox):

• Linux Mint
  • GPU and USB passed though via Virtio with a sata to USB adapter for connecting the bluray drive
  • Used as a desktop and is an alternative to my laptop.
  • It also hosts Jellyfin in a podman container
• Docker 0
  • Nextcloud
• TrueNAS
  • This is a TrueNAS VM with a dedicated sata controller passed though to it. Its used for storage for nextcloud and jellyfin.

Mini PC (proxmox)

• landmass

  • this is a simple LXC container to act as a wireguard client with a caddy proxy. It allows me to access my HDhomerun as it is in another building (long story)

• caddy

  • this used to be for accessing my homerun but is now just for remote access via ssh.

• outside access

  • this is a VM that connects to the VM in linode to route traffic. It runs Ngnix proxy manager and is a wireguard client.

• docker1

  • this hosts Matrix and Drupal. Matrix is basiclly unusable for me because as soon as I start joining rooms the resource usage shoots though the roof and it sometimes crashes

• Linode

  • I have a VM in Linode that routes traffic into outside access via wireguard. It also runs Ngnix proxy manager.

• Friendlywrt

  • I have a Nanopi that acts as a firewall and dhcp server to isolate everything.

This is a incomplete list and doesn't include my firewall rules or other security measures. I also run Debian on all VMs as it is easy to setup and maintain. If you are looking for somewhere to start I would start by installing nextcloud in a docker container. Proxmox will scale the best but if you are just looking to learn I would install Debian and docker compose. TrueNAS is great for a NAS but its designed to be an appliance so it can be limiting.