근데 is a short for 그런데 하지만 means "but, however, though" 그런데 means "well, by the way, anyway, but, however" 그런데 has additional meaning of "by the way" compared to 하지만 In the above sentence, you can substitute 근데 with 하지만.

하지만 is but, 근데 is so,maybe.