I used the cpu/motherboard/ram/psu from a desktop I’d since upgraded, slapped it into a 4u rackmount case I got cheap on Ebay (it looks awful - I think it was previously used in a lab - but it’s solid af), bought a nice big cooler and some noctua fans so it’d run quiet, added an HBA card, 4x shucked 14tb drives and a coupla 1tb m.2s, slapped Unraid on it, and was up and running with an awesome nas for really not that much money. Totally worth it, that thing is awesome.
I will admit it doesn’t look as swanky as a synology, but it was far cheaper, is a lot more capable of non-nas stuff, and every part is standard and upgradeable.
Also if your car is German and the country you’re in is not, you may find yourself in a situation where your car is removed about tyre pressure but the only pump you can find at a petrol station is in PSI and the label is in Bar, and the only way you can convert those is to desperately wave your phone around like a madman trying to get some working internet while freezing cold in the rain. You might be well served by doing that conversion up front and writing it down somewhere.
Totally hypothetical situation, of course.