"I like it the most in open landscapes."
Translation:Jag trivs bäst i öppna landskap.
I absolutely agree. The thing is, though, that trivas is a common word in Swedish which doesn't have a direct equivalent in English. So if we put any of your suggestions, which are all good ones, the most direct translation would be something else. Hence, we need to sacrifice idiomatics for teachability here. It's hardly optimal, though, and we accept a lot more variations when translating from Swedish to English.
I wonder if English sentence has two possible meanings: One that one likes best to be in open landscapes, the other that for example there is a style of garden and I like it the most when it is located in open landscapes. If yes would the second meaning translate to something else than Jag trivs...