I run on old PCs also. Though, I use Proxmox (proxmox uses ZFS, and now that I have expanded to 3 old mini PCs, they can cluster). Not claiming it is superior, it’s probably slightly more complicated, but it works for me. (Also, given the RAM situation, 3 essentially free mini PCs can hold more old salvaged RAM dimms, for more VMs, and redundancy/availability.)

The Proxmox is on the bare metal, then VMs run the heavy applications solo, or docker for stacks of lighter apps kike *arr.

(VMs prevent kernel panic from hitting the host, but containers are lighter, it’s a case by case thing depending on the application/risk. I have had a container take down the host, but for most of us it’s not like we are running critical applications, it’s not a huge deal if you just run containers.)