

Anything on a separate disk can be simply remounted after reinstalling the OS. It doesn’t have to be a NAS, DAS, RAID enclosure, or anything else that’s external to the machine unless you want it to be. Actually it looks like that Beelink only supports a single NVMe disk and doesn’t have SATA, so I guess it does have to be external to the machine, but for different reasons than you’re alluding to.
Personally, I just have a couple of cheap CyberPower UPSs for my servers. I know I know, but I’m waiting for them to get old and die before I replace them with something better. My modem, router, and primary WiFi AP are on a custom LiFePO4-based UPS that I designed and built, because I felt like it. It’ll keep them running for around 10 hours, long past everything else in the house has shut down.