This! Until you have a goal or target functionality the topic is basically unlimited. You can scope into to a Pi-hole and plex/jellyfin server and learn loads
I really want to try using TrueNAS because I feel like learning ZFS. I have raspberry pis but they’re not compatible. I thought about getting a used machine somewhere but wasn’t sure because I will probably end up installing nextcloud and jellyfin on it so I don’t want to worry about hardware bottlenecks