What would be the antonym of the expression "landed with a thud"? I've seen it in the context of "a new product landed with a thud, attracting very few customers".
In this specific context I would suggest "landed with a splash" or (better) "made a splash" as an antonym.
However, this is a metaphorical use of "landed with a thud" which means something almost the opposite of what you would expect from the literal meaning. My suggestions don't apply to more general or literal uses of the phrase. If you really want to talk about an object not making a great deal of noise as it hits the ground, try "landed lightly" or "landed like a cat".
(Having said that, any cat owner will tell you that cats land with an enormous thud. Particularly if they are jumping off a high shelf onto your bed. While you are still in it.)