Debian is kind of the default for many things now, so many guides etc will assume a Debian-like os but if you are familiar with other OSes you can try them just fine. Make sure zfs is supported by the OS properly if you want to use it for your SSDs (which I suggest).

If you are using Docker containers, you can migrate between OSes later relatively easy. Depending on how beefy your optiplex is, you could also use Proxmox as the base os and play with different VMs. Being able to easily snapshot the VMs is pretty great and for me has always been worth the overhead.