Recently I found a simple and cheap solution for integrating current non neutral wired installations by a video from “My Project Box” ( https://youtu.be/xNiywSpqYaY )
For under 10$ per device or better per circuit you can integrate it into homeassistant or any other matter controller.
You can use your current switches and devices ( lamps ) like before, you just add one Sonoff Basic R5 Switch ( Matter over Wifi, costing under 10 $ ). One exception: Pure on-off switches with only one outlet for switched line have to be replaced with a changeover switch.
It works like this: you shortcut both outlets of the physical switch, so that the switched wire is always on with the exception of the short moment the switch is thrown.
In front of the lamp the sonoff switch is positioned. The neutral and the ( now always on ) switched wire power the sonoff, the sonoff switch toggles the lamp when the short break of the thrown physical switch is registered. Due to internal capacitors the sonoff does not lose power in that short moment.
And every matter controller ( e. g. homeassistant, google, alexa ) can also toggle the sonoff and gets state information.
It even works with multiple physical switches ( changeover and cross switches ) in a circuit ( see video ).