just use unraid, I know it's a paid software but much better than OMV, TrueNas is not going to work as it can only do ZFS and ZFS has ECC memory requirements, without ECC chances of data corruption is very high as its very memory dependent, do you trust your old system enough to put data it on it? I've seen TrueNas lose the entire pool during a power outage without no good options to recover from them, with OMV, I faced nothing but issues, be it related to permissions to setup docker containers or install any of the pre-built add-in/extensions, whatever they are call.
so far Unraid for me has been a no-fuss solution. I can mix and match drives and don't need to have all the drives the same size which is a big bonus over other systems.
I am not sharing my experience from way back either, This is recently around 1 year ago, TrueNAS is great if you have the hardware that supports it, including ECC memory, if not, then Unraid is the better solution than anything else out there.