I own this game on Steam and would like to continue playing 1.2.0 . I don't like some changes they made in the latest patch.
On Steam it is possible to rollback game version to 1.1.9.8 in betas, but no option to 1.2.0

Who has this game here on GOG, could you check it out in your GOG Galaxy Manage Installation -> Configure, remove tick in "Auto Updates - Automatically Update to newest version" and see what version you have shown after that.
Does it show 1.2.0 version of the game here?

No, the oldest version is 1.2.0.5.

Thank you! This is great! That's what I needed! I just don't like the 1.2.1 patch and want to rollback it to 1.2.0.x , but not to 1.1.9.8.

Now just waiting for discounts to buy here on GOG!

Just remember that the new expansion will probably need the latest version of the game when it releases in 2025 so if you want to play that you'll have to update then.