FYI,
using HomeWizard P1 Wifi dongle with Aidon 6442 S utility meter, it works with HomeAssistant as expected right out of the box.
Since I’m using this in Finland, Aidon has RJ12 port for HAN P1 interface per SESKO recommendation, no encryption key needed, really plug and play installation. HAN P1 interface is disabled as default (SESKO recommendation) at Aidon meters, I had to call my utility company and they enabled it next day.
HomeWizard P1 Wifi is currently at sale for 24,95€, so I didn’t see much point building reader myself. It’s bargain and ready product, very high quality actually. HomeAssistant has platinum-level integration for HomeWizard, which is able to read power, voltage and current data on all three phases.
Utility companies are usually not much more honest than user car retailers, but my utility company changed meter to newer model for free 
I asked them about their meter changing plans, it would be during next three years, but they said if I order it right away, it can be done during next couple days for free. They were upgrading pricing, and it would cost extra if ordered later, or otherwise, I’d had to wait for scheduled replacement.