Kerbal Space Program: Install older version, and extensions

Hi everyone,

I’m new to Linux and I wanted to try to install one of my favorite game, Kerbal Space Program.

I bought the game on GoG, and I wanted to be able to install an older version of the game, the 1.7.3 (actual is 1.8.1). The reason for that is that I like to play with mods, mostly RP-1, which is not yet compatible with 1.8.x.

On windows in the GoG launcher I can choose the version of the game I can launch.

Here on Linux, with Lutris, I have two issues, the first one is that I did not find any way to install the extensions, Making History, and Breaking Ground.
The second is that I did not find any way to install an older version of the game.
To solve the first issue, I downloaded the extension installer from the GoG website and installed them in the same folder as the Lutris install, and the gave ownership of the new folders to user.

But for the version I’m a bit stuck, anyone could help me?

Thanks