I recently acquired a TerraMaster F5-221 to replace two older NAS (a ReadyNAS and a Synology) that were running in parallel. Nothing really wrong with that except maybe for power consumption. However, when the OpenVPN started to act weird on both NAS, I decided an upgrade would be nice. According to reviews, the TerraMaster F5-221 has nice hardware (Intel Apollo J3355) but poor software, which is a quite common story when it comes to NAS, it seems. It was clear I would replace the OS with something like TrueNAS or openmediavault which have open source roots, but in my research I found Unraid was mentioned quite a lot. Unraid is closed source, it's not free, but it's not very expensive either and it's based on Linux. Also, the app ecosystem is actually based on Docker, which is neat!