the ∆v makes a sample return mission from an interstellar object currently impossible. 3l atlas is doing 63kilometers/second and anything even going whatever the minimum speed to qualify as interstellar will be goiing to fast to catch up to, and then have enough fuel to brake for a gravitational capture by the sun. our best chance to learn about interstellar objects is to blast them with ultra high powered laser beams and use telescopes to do remote spectrographic and visual analysis , this could likely be cobbled together right now.
You can leave off the laser beams and just look at them with telescopes. The paper we're discussing is exactly that.
we can do much more with direct laser strikes, a laser will be able to blast through the dust and gass corona, if there was radar directed at the same time for precise timing and targeting. size, velocity, shape, and details of its shape, and composition in many areas and reach below the imediate surface we cant catch it, but we can certainly get a much better look