I had a downdraft table for a few years (20 years ago) connected to my dust collection system. Note the past tense. The bottom line is that in a home workshop environment they are a great idea but In my case at least never seemed to work well enough to justify the bother.
Sure you could remove dust, as long as you were only dealing with a small object and kept it above the table. If I was a model maker with a lot of hand sanding of small objects I’d consider it, but not for anything else.
In my shed a proper shopvac attachment to the sander removes a significant amount of the problem. A good bellmouth over the bench connected to a 2.5hp collector takes a lot of airborne dust, extractor fans keeps air turning over.
Then an air filter takes care of the rest!
https://www.prusaprinters.org/prints/129038-dust-collecton-150mm-6-inch-bellmouth