… and backups.
I have a device comparable to the Librem Mini that I use as a low budget home server. It has been running 24x7 for the last 7 years or so, with many short outages for reboot after updates, regular moderate length outages for offline backups, and the occasional outage due to mains power outage (exceeding run time on the UPS, but not since I’ve had the PV system with battery, although the PV system was purchased for the general benefit of the household, and the benefit to reliability of mains power is an added bonus).
This is adequate for my needs. It’s not like I’m operating an online store and will lose a zillion dollars an hour if the server is down …
However I think one has to be realistic about getting what one is paying for. Server-class hardware may have vastly more redundancy in a range of areas whether it’s multiple CPUs, ECC memory, multiple power supplies, …
At the very least, you need to ask yourself: what is my plan if the hardware fails?
You should also think about your disk storage. I think I am right in saying that most spinning rust disks are not rated for 24x7 operation, well not consumer-level disks anyway. So if the amount of storage that you want is not vast, you would probably want SSDs and regardless you would want storage redundancy (RAID etc.).