hi everyone I wanted to know if it was possible to use home assistant if I have devices in two houses separated by many km, to be able to manage the devices from a single interface
Yes, it’s possible.
I indeed have three houses with only one HA in a RPi4 in one of them.
I have a bunch of temperature/humidity, movement sensors and a lot of switches, most of them from Sonoff, and some actuators (water valves).
If this helps you, I use SonoffLAn integration which allows local and cloud devices from Sonoff (Ewelink app).
If you mean can you join two or more “Home Assistant” instances together, so you only need to log into one to get all the sensors, & control every thing? Yes, Remote Home Assistant.
Otherwise it depends on the “Devices”, “Bridges” & “Gateways” you use.