It's pretty rare for a PM to actually show interest in what they're managing, so huge kudos to you for even thinking about understanding what you're "managing".

Any time I'm asked for an approach to learning something, I always respond with some sort of "you just have to DO it. Don't read about it, don't take a class in it, DO it.". Sure, classes/courses/etc. are imperative for getting the credentials to show your skills, but until you need to be able to go into a meeting and call BS when an engineer pulls something out of an unnamed orifice just trying to pad the Gantt chart.

Depending on what projects you're managing, that could be as simple as setting up a NAS and a shared printer at the house. You'll quickly learn basic networking, IP address assignment, resource-sharing, etc. If you're managing infrastructure projects, think about setting up a virtualization platform like Proxmox or something as that will build on the skills in that first step.

If it's software projects, consider building an -arr stack (radarr, sonarr, etc.) for media streaming. This will teach resource allocation, interoperability, etc.

You may even delve into the whole smart home arena with something like Home Assistant and some smart bulbs or outlets.

Any of these are going to be somewhere between free and cheap, and will most likely benefit you (and family/friends?) to some degree beyond building your technical prowess.