"The solution is trivial: [possible solution]! Well, unfortunately, [problem with solution]."
The issue here isn't so much sarcasm than that "is" should be read as "seems" here. But I don't see any other idiomatic reading that is sincerely calling the solution trivial.
The issue here isn't so much sarcasm than that "is" should be read as "seems" here. But I don't see any other idiomatic reading that is sincerely calling the solution trivial.