

Why does everyone think the term came from Star Wars? I know it was used in steampunk before then, and google suggests it goes back to a 1958 article about robots. Sorry, not trying to be pedantic, just feels like a lot of people give Star Wars unjust credit for things they didn’t actually create.
I think my suggestion would be to use the PC as a dedicated firewall, but you will need at least two ethernet ports for that (one to connect to the ISP router, and the second for internal network). This lets you learn network security and control the traffic that can actually get to your other computers. You could also set up KVM to start running virtual machines here. The idea with a VM is to keep services separate and isolated, so like one VM to manage security cameras, another VM to host a game server, another one to host sonarr/radarr/jellyfin… etc.
When you are able to expand, your second physical machine should be your NAS. Get your storage space started, share it over NFS or samba, and move your backup/security camera/sonarr VMs over to this machine for direct access to the larger storage space. Pay attention to system usage and move your VMs to balance the cpu/memory resources. Eventually you may want to get a third machine dedicated more for hosting the game servers, maybe a web server to view the security camera feeds, or whatever.
You mentioned backing up Wikipedia… Have a look at the Kiwix project, you can already get access to regular backups for a lot of information sites.