Joining 2 HA instances running in different houses in 1 Lovelace

I would like to see experiences of people who already has done it. I could not find information about it here.
Ways to join the networks (OpenVPN, Wireguard, PPTP), bridging MQTT servers and recreating sensor in the other end and better ways of doing all of this.
All experiences are welcome.

Use mqtt_statestream ?

It seems to me that mqtt bridge makes more sense. Search for “Configuring Bridges”.