Two Home Assistant, one way control

I have a HA at my main house and I also bought another HA for my summer house that I share with a friend.

I would like to connect the two HA if it possible and from my house get all inputs from the summer house and use them for example turn on a light in my main house.

But I do not want my friend to take control or mess with my HA in the main House from the HA in the summer house, so maybe it is not possible.
I was thinking like one-way communication, I can control the Ha at the summer house but, the Ha in the summer house should not be able to control my HA in the main house.
Like a master and slave, same as when you connect some other electric equipment.

I can not use a normal VPN because I do not get a public IP address from the internet provider company, but Tailscale works and can be installed on both HA.

So what would be possible or can you see other solutions