That absolutely works, but when I built my offsite backup to hetzner I also thought about setting up own hardware and came to conclusion that for myself it doesn't really make a ton of sense. New RPi + 4TB ssd/m.2 drive with accessories adds up to something around 400€ (if that's even enough today), or few years worth of cloud backups. With own hardware there's always need to maintain it and hardware failures are always an option, so for me it makes more sense to just rely on big players with offsite backups. Your case might be different for various reasons, but sometimes renting capacity just makes more sense in the big picture.