Bell wire is really thin and you can run a low voltage line around your house that is nearly invisible. That's the old school, physical option and is not to be sniffed at if it does the job.

If you want to get something safe and smart (IoT) then you have to think like an engineer. You also need to decide if you are going to do one thing - a doorbell, or if you want disco lights by the pool and the rest.

For a doorbell, you need a button at the door and a chime or whatever inside the house to indicate the button has been pushed. Already you have to potentially deal with delivering power at a place that might be hard, door frames/walls, wires, batteries, weather, positioning and lots more. Then you need to get the signal to a chime.

My previous doorbell was a chime that I wired into a switched and fused spur (I ran a 5A rated twin and earth out of a light socket into a back box with a switched socket faceplate and it has its own fuse) into the nearest lighting socket and a bell wire that ran out to the button. That was fine and simple but not too smart!

I have PoE switches and my IT gear is mostly in the attic. I put a backbox with an ethernet socket in the attic and ran solid core down through the roof/wall etc to near to where the door bell is on the inside of my house and put another backbox with ethernet face plate on it. I then run a short (3m) patchlead inside some trunking and through the front door frame and into the back of a Reolink PoE powered doorbell. I also have Home Assistant running as a VM on a Proxmox box.

Somewhere between those two setups sounds like where you want to go. I went for PoE because I also have UPS for my switches and other infra but wifi may be fine for you for comms but you still have to do power and I'm not a fan of battery powered door buttons but that might be a design decision for you.

You mention VLANs and I really recommend that you look into them. They are a core building block of networking. However, I also get that becoming a network expert is not on everyone's score card. Then again, you are hanging around on HN and probably tending towards ... nerd!

Even a simple doorbell can become pretty sodding complicated and that is why we have some people wondering what on earth all the fuss is about and others advocating to smash the looms ... sorry, doorbells.