At the risk of leaking info to any toes I step on w.r.t my home environment,

- home assistant - Network Video Recorder - Jellyfin - network management such as ubiquiti or omada etc - vault warden/1pass/other secrets servers - tailscale or wire guard server - build server/k8s test environment - private artifactory or mirror (especially useful if you're using the same distro on a bunch of devices but don't want to overload the actual mirror+improves download times) - torrents (someone's gotta seed Wikipedia) - onsite backups - bastion into your home network (see also: wire guard) - some people even use it for their router

You could also take a look at the tteck scripts, there's a bunch of cool stuff in there