Wifi is fine for some things, but it’s power hungry, it requires an IP address for each device, and is subject to interference from other wifi devices. If you want to block all of the devices from accessing the internet, it adds some extra complexity. If you have a battery powered wifi device, it will power itself off until activated, then have to connect to your wireless network (DHCP, etc) before it can transmit, which takes a second or three.

ZigBee, ZWave, and BLE are low power protocols, and are fairly statically configured. They use less power and can have much better battery life on much smaller batteries. When activated, they connect back to their respective networks immediately, so things like smart buttons and motion sensors are very fast.

What about using a Shelly relay with power monitoring, and installing it inside the outlet?

I have a few Shelly 1PM Pluses that I do this with, but Shelly is starting to make ZigBee and ZWave devices too. I haven’t looked to see if they have a ZigBee one with power monitoring, but I’d bet they do.

Another option is something like using an Emporia Vue 2 or a system from Circuit Setup to monitor power from your breaker panel. Both can be flashed with ESPHome and record directly to HA. Not sure how well they work in the EU, but I’m planning on getting an Emporia Vue 2 here in the US.

Smart switches and local automations are the key, not smart bulbs in the cloud.

Every light in my house is smart in one way or another, but if HomeAssistant and my internet connection both went down, basically everything would still function totally normally. Light switches would still turn on lights, etc. They’d just lose their voice control and wouldn’t be turned on by motion sensors, etc.

I do have some smart bulbs in the house, but they’re in accent lighting (pendants, etc), they run 100% locally, and they’re turned on and off by automations that are triggered by physical light switches. For example, you turn on the main kitchen lights with the smart switch, and that triggers the pendants to turn on. Its reliable enough that I’ve only seen the bulbs miss a trigger or get out of sync twice in two years, and toggling the light switch and extra time fixed it both times. If the bulbs ever had a network issue (which they haven’t), they’re accessible without a ladder or much fuss, and can be easily unscrewed/reseated for a power cycle.

My family doesn’t share my interest in home automation, but as long as everything works reliably and in an intuitive way, they’re fine with it.