A custom Arch install is what I have on my router.
There's no real auto-update for Arch, and it wasn't designed for it (IIRC according to their forums/wiki), so I have to login every now and then and run pacman (I'll admit I haven't invested more than a couple hours searching).
The `kea` package (DHCP server) got updates this summer, 3 weeks apart, that both broke configuration file parsing, and I had to discover the next day on reboot. "But you should have read the changelog!", "But you should have tested the config files on updates!", "But you should have restarted the service!" ...: no, no I don't normally test every config file or restart every service after an upgrade, and I don't normally read Changelogs of all software installed on my machines. I shouldn't have to do that in 2025.
`zfs` is out of kernel, I've dabbled with that for a while until I understood if you want your machine to reboot 100% of the times, you'd better stick with in-kernel filesystems, no matter how worse featureset they have.
Sometimes stuff will just break on package upgrades without notice or warning, and you're left to pick up the pieces, normally in a hurry because your partner is screaming at you.
Compare that with Synology, where I have never, ever needed to login to click "run updates" or put it in "maintenance mode" to fix it. It updates itself, it boots at the set time, it brings up all services, runs periodic scrubbing, informs me via mail, shuts down at the specified time. It has a 2x-SSD mirror for cache, and I don't need to care about the disk layout and configuration, and the cache configuration, .....
It's literally a set-and-forget auto-upgrading box that I can just use instead of maintain.
I understand that Synology is not in good shape anymore, see my other top-comment :)