I understood that the dust issue was limited to the first run or so of the Q line, and that dust was coming in the battery door. Leica later added a gasket to that to that area to minimize the issue. With a camera that price I would not be putting tape over holes and destroying the function and looks (and resale value). The tape will attract dirt, dust, sand, etc. along the edges and will leave abrasions, in addition to the sticky tape residue.
I agree with this based on my own experience with a dusty-sensor Q.
I had a Q that I bought second hand, that arrived with a severe dust issue despite the seller having told me the sensor was clean (I think she only ever shot it wide-open). It was a good buy, though, so I kept it and sent it to Leica in NJ for cleaning.
During that process I exchanged email with a Leica tech who explained that the first two years of Q cameras (mid-2015 intro through mid-2017 produced cameras) are the ones with the dust problem. Starting in mid-2017, he said Leica added a “dust shroud” to the Q design to prevent the ingress of dust that had affected many Q cameras.
So cameras with a production date after mid-2017 were manufactured with the updated design including dust shroud. Those manufactured prior to mid-2017, which mine was, were/are retrofitted with the dust shroud as they come in for CLA/sensor cleaning service. The tech noted specifically, since I asked, that the dust was *not* entering the cameras through the mic holes, so the popular “tape the holes” practice isn’t effective. Personally I’d be concerned about those tiny holes filling up with tape residue as the tape breaks down over time, as well as grunge along the edge of the tape as theory03 notes.
So based on my experience, if buying a used one now I’d seek out a body that was either produced after mid-2017, or that is an earlier one with documentation for having been in for the service. “Install dust shroud” is itemized on the Leica work-order paperwork (at least it was on mine). Either of these conditions should get you a camera much more likely to be dust-free, though I have no idea how effective the dust shroud is over the long-term.
I loved my Q, however I sold it after a while to fund an M lens. I’ve missed it, though, and I’ve recently been considering picking up another. May go for a Q-P this time. My understanding is that all of those have the dust shroud (production started in 2018).