I did that too but those PCs are just stupidly massive for the purpose. Raspberry Pi 4s don’t require SD cards any more so the storage issue is moot. My RPi sits next to my router now, you wouldn’t even know it’s there unless you looked closely.
Pi will be single purpose device, the "micro" can be full blown server and comes with ALL parts required, no need to hunt for good PSU, case, cooling, storage. Some of them come with 1 Sata and 2x M.2 NVMe, so you can literally pass those NVMe to TrueNAS in proxmox and run full blown NAS with encryption/encoding/decoding in VM.
Some brave souls have installed Home Assistant on their routers: https://www.snbforums.com/threads/home-assistant-entware-gt-...