I have an HP Proliant G2 tower server case from the early 2000s. Its got 9 drive bays (if you include the floppy drive bay).

Hilariously, it’s ATX compatible, so I stuffed it with an older Asus motherboard (7th gen Intel + i7-7700T, w/NVME slot), 16GB DDR4 RAM, ~650W ATX PSU, and an LSI SAS card. Now I just need to migrate everything over to it from my older Mac Mini that’s currently serving as the NAS…