For my single self-hosted server (also NixOS), I use netdata, because it has all the info I need, is efficient enough while keeping a day’s worth of history as well, and most importantly has built-in alerts for services like telegram or slack.
Other stacks can do the same, but I haven’t found anything as simple to set up; netdata is just a simple service.
My first exposure to netdata was part of the default FreeNAS install. It was super easy to use and effective to understand the basic server health and telemetry.
Simple yes; simplistic no.
It can provide you with thousands of metrics you never thought of monitoring. On top of that comes with pre-configured alerts, eBPF support, metric correlations and anomaly rates for every single metric it collects.
I think there's a pretty large middle ground between what I'd consider a home server setup (or self hosting it wherever) and practicing for enterprise tasks.
Much of the crowd around here and certain subreddits IS probably practicing for more, but I have a counterexample. You won't find him around the internet. Not interested.
I have a friend who's recently learned just enough Linux and Docker to get through a Debian install with some prompting, and run a Matrix home server, Nextcloud and Jellyfin because he thought they were cool. Its an old (for him) repurposed desktop.
He's a mechanic. He doesn't care about anything enterprise. He doesn't want monitoring because he'll know if it's down. He doesn't care if backups run because he's sure he's got the important stuff on an old disk somewhere, probably.
Other stacks can do the same, but I haven’t found anything as simple to set up; netdata is just a simple service.