I wonder what's the cheapest way to make an efficient NAS, if your router doesn't have a good USB port or doesn't have a good SMB server (mikrotik 😒).

Raspberry pis and such sbcs are overpriced cause everyone does everything with them. Maybe get an old used high-end AC router that has good hardware and can be flashed with openwrt?

There's also old PCs like old scrap laptops, but they're not so power efficient, so they're not good for idling 24/7, which you would need for time machine backup. Or is there a way to wake on any LAN instead of magic packet?