DietPi VS OpenMediaVault

DietPi is a lightweight Debian based Linux distribution for SBCs and server systems, with the option to install desktop environments, too. It ships as minimal image but allows to install complete and ready-to-use software stacks with a set of console based shell dialogs and scripts.

The source code is hosted on GitHub: https://github.com/MichaIng/DietPi

That's a good point, but the array of devices supported by the DietPi team is extensive: https://dietpi.com/

Before someone starts the usual yadda yadda about the RPi biger community, the OS not having long time support etc. I would repeat one more time: do not rely on board vendor supplied images; this is valid for pretty much all boards. Just go to Armbian or DietPi pages and you'll almost certainly find one or more images that work on your board and forums to discuss about them with very knowledgeable people.

https://www.armbian.com/download/

https://dietpi.com/#download

Those projects are well worth a contribution, as they don't have a giant like Broadcom behind them.

> bananapi do a lot of boards but their software story has been a bit poor

This is quite common with other board manufacturers too. I'd rather suggest to ignore completely their cobbled together distros, often also tainted by proprietary modifications, that become unmaintained in a few years, and see if they're among the many supported by Armbian or DietPi.

https://www.armbian.com/download/

https://dietpi.com/#download

The full release notes can be found at: https://dietpi.com/docs/releases/v8_25/

RPi OS = diet pi https://dietpi.com/ - initial config via text file - SDcard burning out partially mitigated as writes log files to ram then flushes to SDcard reducing write cycles

You could also try very minimalistic distros like TwisterUI or DietPi which are most known for their use in the RasprebbyPi / SBC computers but which also have editions for desktop / laptop.

You might want to consider the previously mentioned MergerFS and SnapRAID, or MDADM and LVM for your setup. OpenMediaVault [https://www.openmediavault.org/ is a solid choice in this regard. Additionally, if you're planning to run something like Proxmox, you could look into deploying Starwind CVM on top of it. Pretty much like in this guide: https://www.starwindsoftware.com/resource-library/starwind-virtual-san-vsan-configuration-guide-for-proxmox-vsan-deployed-as-a-controller-virtual-machine-cvm/ .

You would better to install OMV instead. It's a ready to use fileserver solution with web interface.

So I'm working on a similar setup with an ancient desktop my in-laws were getting rid of. I installed OpenMediaVault directly to the hard drive (it's so old that I assume it wouldn't work too well as a hypervisor), with a 4TB external HDD attached. OMV supports Docker by means of a plug-in and I'm running a Jellyfin container with no issues at all. I'm still manually downloading everything to the HDD but *arr containers are my next step, as well as setting up a gluetun container to route all that through a VPN.

That is possible (it's automated to a certain extent). It also depends on the NAS OS. Unraid, for example, can work with drives of different sizes while using the largest one for parity. TrueNAS uses ZFS so you won't be able to just add a drive to your RAIDZ and expand it. There's also openmediavault: https://www.openmediavault.org/ that uses Linux Software RAID and you can add a new drive there but you can't combine drives of different sizes. And there's also Starwinds NAS that supports both Linux Software RAID and ZFS: https://www.starwindsoftware.com/san-and-nas. Plus, I would avoid SMR drives in RAID: https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-drives-hdd/

I'd put it like that: if you have a spare PC, then it's definitely worth trying. I would also look into openmediavault (minimal RAM needs): https://www.openmediavault.org/ and Starwinds NAS (supports both ZFS and Linux software RAID): https://www.starwindsoftware.com/san-and-nas

Your current PC looks very decent for a lab. Proxmox on it, then one Linux VM with Docker, another VM for NAS with something lite and easy like openmediavault: https://www.openmediavault.org/ or Starwinds NAS: https://www.starwindsoftware.com/san-and-nas and Plex separately. And other stuff in VMs or containers.