A Pfsense/opnsense VM taught me how networking works. Before I set it up, all I knew about was port forwarding. I learned about firewall rules, LAN and WAN, VLANs, VPNs, DNS, Dynamic DNS, reverse proxies, bufferbloat, DHCP, etc.
I’m also learning how to make my own CI/CD pipelines with self hosted GitHub Actions as well as dockerizing applications.